Rudolf Rocker was born to the lithographer Georg Philipp Rocker and his wife Anna Margaretha née Naumann as the second of three sons in Mainz, Hesse (now Rhineland-Palatinate), Germany on March 25, 1873. This Catholic, yet not particularly devout, family had a democratic and anti-Prussian tradition dating back to Rocker's grandfather, who participated in the March Revolution of 1848. However, Georg Philipp died just four years after Rocker's birth. After that, the family managed to evade poverty, only through the massive support by his mother's family. Rocker's uncle and godfather Carl Rudolf Naumann, a long-time member of the Social Democratic Party (SPD), became a substitute for his dead parents and a role model, who directed the boy's intellectual development. Rocker was disgusted by his schoolteacher's authoritarian methods calling the man a "heartless despot". He was, therefore, a poor student. When he was ten, the Rocker household was joined by his mother's new husband Ludwig Baumgartner. Rocker was shocked once again as his mother died in February 1877. After his stepfather re-married soon thereafter, Rocker was put into an orphanage.

Disgusted by the unconditional obedience demanded by the Catholic orphanage and drawn by the prospect of adventure, Rocker ran away from the orphanage twice. The first time he just wandered around in the woods around Mainz with occasional visits to the city to forage for food and was retrieved after three nights. The second time, which was at the age of fourteen and a reaction to the orphanage wanting him to be apprenticed as a tinsmith, he worked as a cabin-boy for Köln-Düsseldorfer Dampfschiffahrtsgesellschaft. He enjoyed leaving his hometown and traveling to places like Rotterdam. After he returned, he started an apprenticeship to become a typographer like his uncle Carl.

Carl also had a substantial library consisting of socialist literature of all colors. Rocker was particularly impressed by the writings of Constantin Franz, a federalist and opponent of Bismarck's centralized German Empire; Eugen Dühring, an anti-Marxist socialist, whose theories had some anarchist aspects; novels like Victor Hugo's Les Misérables and Edward Bellamy's Looking Backward; as well as the traditional socialist literature such as Karl Marx's Capital and Ferdinand Lasalle and August Bebel's writings. Although Rocker is unlikely to have grasped all of the political and philosophical implications of what he read, he became a socialist and regularly discussed his ideas with others. His employer became the first person he converted to socialism.

Under the influence of his uncle, he joined the SPD and became active in the typographers' labor union in Mainz. He volunteered in the 1890 electoral campaign, which had to be organized in semi-clandestinity because of continuing government repression, helping the SPD candidate Franz Jöst retake the seat for the district Mainz-Oppenheim in the Reichstag. Because the seat was heavily contested, important SPD figures like August Bebel, Wilhelm Liebknecht, Georg von Vollmar, and Paul Singer visited the town to help Jöst and Rocker had a chance to see them speak.

In 1890, there was a major debate in the SPD about the tactics it would choose after the lifting of the Anti-Socialist Laws. A radical oppositional wing known as Die Jungen (The Young Ones) developed. While the party leaders viewed the parliament as a means of social change, Die Jungen thought it could at best be used to spread the socialist message. They were unwilling to wait for the collapse of capitalist society, as predicted by Marxism, rather they wanted to start a revolution as soon as possible. Although this wing was strongest in Berlin, Magdeburg, and Dresden, it also had a few adherents in Mainz, among them Rudolf Rocker. In May 1890, he started a reading circle, named Freiheit (Freedom), to study theoretical topics more intensively. After Rocker criticized Jöst and refused to retract his statements, he was expelled from the party. The same would happen to the rest of Die Jungen in October 1891. Nonetheless, he remained active and even gained influence in the socialist labor movement in Mainz. Although he had already encountered anarchist ideas as a result of his contacts to Die Jungen in Berlin, his conversion to anarchism did not take place until the International Socialist Congress in Brussels in August 1891. He was heavily disappointed by the discussions at the congress, as it, especially the German delegates, refused to explicitly denounce militarism. He was rather impressed by the Dutch socialist and later anarchist Domela Nieuwenhuis, who attacked Liebknecht for his lack of militancy. Rocker got to know Karl Höfer, a German active in smuggling anarchist literature from Belgium to Germany. Höfer gave him Bakunin's God and the State and Kropotkin's Anarchist Morality, two of the most influential anarchist works, as well as the newspaper Autonomie.

Rocker became convinced that the source of political institutions is an irrational belief in a higher authority, as Bakunin claimed in God and the State. However, Rocker rejected the Russian's rejection of theoretical propaganda and his claim that only revolutions can bring about change. Nevertheless, he was very much attracted by Bakunin's style, marked by pathos, emotion, and enthusiasm, designed to give the reader an impression of the heat of revolutionary moments. Rocker even attempted to emulate this style in his speeches, but was not very convincing. Kropotkin's anarcho-communist writings, on the other hand, were structured logically and contained an elaborate description of the future anarchist society. The work's basic premise, that an individual is entitled to receive the basic means of living from the community independently of his or her personal contributions, impressed Rocker.

In 1891, all Die Jungen were either expelled from the SPD or left voluntarily. They then founded the Union of Independent Socialists (VUS). Rocker became a member and founded a local section in Mainz, mostly active in distributing anarchist literature smuggled in from Belgium or the Netherlands in the city. He was a regular speaker at labor union meetings. On December 18, 1892, he spoke at a meeting of unemployed workers. Impressed by Rocker's speech, the speaker that followed Rocker, who was not from Mainz and therefore did not know at what point the police would intervene, advised the unemployed to take from the rich, rather to starve. The meeting was then dissolved by the police. The speaker was arrested, while Rocker barely escaped. He decided to flee Germany to Paris via Frankfurt. He had, however, already been toying with the idea of leaving the country, in order to learn new languages, get to know anarchist groups abroad, and, above all, to escape conscription.

In Paris, he first came into contact with Jewish anarchism. In Spring 1893, he was invited to meeting of Jewish anarchists, which he attended and was impressed by. Though neither a Jew by birth nor by belief, he ended up frequenting the group's meeting, eventually holding lectures himself. Solomon Rappaport, later known as S. Ansky, allowed Rocker to live with him, as they were both typographers and could share Rappaport's tools. During this period, Rocker also first came into contact with the blending of anarchist and syndicalist ideas represented by the General Confederation of Labor (CGT), which would influence him in the long term. In 1895, as a result of the anti-anarchist sentiment in France, Rocker traveled to London to visit the German consulate and examine the possibility of his returning to Germany but was told he would be imprisoned upon return.

Rocker decided to stay in London. He got a job as the librarian of the Communist Workers' Educational Union, where he got to know Louise Michel and Errico Malatesta, two influential anarchists. Inspired to visit the quarter after reading about "Darkest London" in the works of John Henry Mackay, he was appalled by the poverty he witnessed in the predominantly Jewish East End. He joined the Jewish anarchist Arbeter Fraint group he had obtained information about from his French comrades, quickly becoming a regular lecturer at its meetings. There, he met his lifelong companion Milly Witkop, a Ukrainian-born Jew who had fled to London in 1894. In May 1897, having lost his job and with little chance of re-employment, Rocker was persuaded by a friend to move to New York. Witkop agreed to accompany him and they arrived on the 29th. They were, however, not admitted into the country, because they were not legally married. They refused to formalize their relationship. Rocker explained that their "bond is one of free agreement between my wife and myself. It is a purely private matter that only concerns ourselves, and it needs no confirmation from the law." Witkop added: "Love is always free. When love ceases to be free it is prostitution." The matter received front-page coverage in the national press. The Commissioner-General of Immigration, the former Knights of Labor President Terence V. Powderly, advised the couple to get married to settle the matter, but they refused and were deported back to England on the same ship they had arrived on.

Unable to find employment upon return, Rocker decided to move to Liverpool. A former Whitechapel comrade of his persuaded him to become the editor of a recently founded Yiddish weekly newspaper called Dos Fraye Vort (The Free Word), even though he did not speak the language at the time. The newspaper only appeared for eight issues, but it led the Arbeter Fraint group to re-launch its eponymous newspaper and invite Rocker to return to the capital and take over as its editor. Although it received some funds from Jews in New York, the journal's financial survival was precarious from the start. However, many volunteers helped by selling the paper on street corners and in workshops. During this time, Rocker was especially concerned with combating the influence of Marxism and historical materialism in London's Jewish labor movement. In all, the Arbeter Fraint published twenty-five essays by Rocker on the topic, the first ever critical examination of Marxism in Yiddish, according to William J. Fishman. Arbeter Fraint's unsound financial footing also meant Rocker rarely received the small salary promised to him when he took over the journal and he depended financially on Witkop. Despite Rocker's sacrifices, however, the paper was forced to cease publication for lack of funds. In November 1899, the prominent American anarchist Emma Goldman visited London and Rocker met her for the first time. After hearing of the Arbeter Fraint's situation she held three lectures to raise funds, but that was not enough.

Not wanting to be left without any means of propaganda, Rocker founded the Germinal in March 1900. Compared to Arbeter Fraint, it was more theoretical, applying anarchist thought to the analysis of literature and philosophy. It represented a maturation of Rocker's thinking towards Kropotkin-ite anarchism and would survive until March 1903. 1902 saw the London Jews being targeted by a wave of anti-alien sentiment, while Rocker was away for a year in Leeds. Upon return in September, he was happy to see the Jewish anarchists had kept the Arbeter Fraint organization alive. A conference of all Jewish anarchists of the city on December 26 decided for a re-launch of the Arbeter Fraint newspaper as the organ of all Jewish anarchists in Great Britain and Paris and made Rocker the editor. The first issue appeared on March 20, 1903. Following the Kishinev pogrom in the Russian Empire, Rocker led a demonstration in solidarity with the victims, the largest ever gathering of Jews in London. Afterwards he traveled to Leeds, Glasgow, and Edinburgh to lecture on the topic.

From 1904, the Jewish labor and anarchist movements in London reached their "golden years", according to William J. Fishman. In 1905, publication of Germinal resumed, it reached a circulation of 2,500 a year later, while Arbeter Fraint reached a demand of 5,000 copies. In 1906, the Arbeter Fraint group finally realized a long-time goal, the establishment of a club for both Jewish and gentile workers. The Workers' Friend Club was founded in a former Methodist church on Jubilee Street. Rocker, by now a very eloquent speaker, became a regular speaker. As a result of the popularity of both the club and Germinal beyond the anarchist scene, Rocker befriended many prominent non-anarchist Jews in London, among them the Zionist philosopher Ber Borochov.

From June 8, 1906, Rocker was involved in a garment workers' strike. Wages and working conditions in the East End were much lower than in the rest of London and tailoring was the most important industry. Rocker was asked by the union leading the strike to become part of the strike committee along with two other Arbeter Fraint members. He was a regular speaker at the strikers' gatherings. The strike failed, because the strike funds ran out. By July 1, all workers were back in their workshops.

Rocker represented the federation at the International Anarchist Congress in Amsterdam in 1907. Errico Malatesta, Alexander Shapiro, and he became the secretaries of the new Anarchist International, but it only lasted until 1911. Also in 1907, his son Fermin was born. In 1909, while visiting France, Rocker denounced the assassination of the anarchist pedagogue Francisco Ferrer, leading him to be deported back to England.

In 1912, Rocker was once again an important figure in a strike by London's garment makers. In late April, 1,500 tailors from the West End, who were more highly skilled and better-paid than those in the East End, started striking. By May, the total number was between 7,000 and 8,000. Since much of the West Enders' work was now being performed in the East End, the tailors' union there, under the influence of the Arbeter Fraint group, decided to support the strike. Rudolf Rocker on the one hand saw this as a chance for the East End tailors to attack the sweatshop system, but on the other was afraid of an anti-Semitic backlash, should the Jewish workers remain idle. He called for a general strike. His call was not followed, since over seventy percent of the East End tailors were engaged in the ready-made trade, which was not linked with the West End workers' strike. Nonetheless, 13,000 immigrant garment workers from the East End went on strike following a May 8 assembly at which Rocker spoke. Not one worker voted against a strike. Rocker became a member of the strike committee and chairman of the finance sub-committee. He was responsible for collecting money and other necessities for the striking workers. On the side he published the Arbeter Fraint newspaper on a daily basis to disseminate news about the strike. He spoke at the workers' assemblies and demonstrations. On May 24 a mass meeting was held to discuss the question of whether to settle on a compromise proposed by the employers, which did not entail a closed union shop. A speech by Rocker convinced the workers to continue the strike. By the next morning, all of the workers' demands were met.

Rocker opposed both sides in World War I on internationalist grounds. Although most in the United Kingdom and continental Europe expected a short war, Rocker predicted on August 7, 1914 "a period of mass murder such as the world has never known before" and attacked the Second International for not opposing the conflict. Rocker with some other Arbeter Fraint members opened up a soup kitchen without fixed prices to alleviate the further impoverishment that came with the Great War. There was a debate between Kropotkin, who supported the Allies, and Rocker in Arbeter Fraint in October and November. He called the war "the contradiction of everything we had fought for". Shortly after the publication of this statement, on December 2, Rocker was arrested and interned as an enemy alien. This was also the result of the anti-German sentiment in the country. Arbeiter Fraind was suppressed in 1915. The Jewish anarchist movement in Britain never fully recovered from these blows.

In March 1918, Rocker was taken to the Netherlands under an agreement to exchange prisoners through the Red Cross. In Holland, he stayed at the house of the socialist leader Domela Nieuwenhuis. There he recovered from the health problems he suffered from as a result of his internment in the UK and met up with his wife Milly Witkop and his son Fermin. He returned to Germany in November 1918 upon an invitation from Fritz Kater to join him in Berlin to re-build the Free Association of German Trade Unions (FVdG). The FVdG was a radical labor federation that quit the SPD in 1908 and became increasingly syndicalist and anarchist. During World War I, it had been unable to continue its activities for fear of government repression, but remained in existence as an underground organization.

Rocker was opposed to the FVdG's alliance with the communists during and immediately after the November Revolution, as he rejected Marxism, especially the concept of the dictatorship of the proletariat. Soon after arriving in Germany, however, he once again became seriously ill. He started giving public speeches in March 1919, including one at a congress of munitions workers in Erfurt, where he urged them to stop producing war material. During this period the FVdG grew rapidly and the coalition with the communists soon began to crumble. Eventually all syndicalist members of the Communist Party were expelled. From December 27 to December 30, 1919, the twelfth national congress of the FVdG was held in Berlin. The organization decided to become the Free Workers' Union of Germany (FAUD) under a new platform, which had been written by Rocker: the Prinzipienerklärung des Syndikalismus (Declaration of Syndicalist Principles). It rejected political parties and the dictatorship of the proletariat as bourgeois concepts. The program only recognized de-centralized, purely economic organizations. Although public ownership of land, means of production, and raw materials was advocated, nationalization and the idea of a communist state were rejected. Rocker decried nationalism as the religion of the modern state and opposed violence, championing instead direct action and the education of the workers.

On Gustav Landauer's death during the Munich Soviet Republic uprising, Rocker took over the work of editing the German publications of Kropotkin's writings. In 1920, the social democratic Defense Minister Gustav Noske started the suppression of the revolutionary left, which led to the imprisonment of Rocker and Fritz Kater. During their mutual detainment, Rocker convinced Kater, who had still held some social democratic ideals, completely of anarchism.

In the following years, Rocker became one of the most regular writers in the FAUD organ Der Syndikalist. In 1920, the FAUD hosted an international syndicalist conference, which ultimately led to the founding of the International Workers Association (IWA) in December 1922. Augustin Souchy, Alexander Schapiro, and Rocker became the organization's secretaries and Rocker wrote its platform. In 1921, he wrote the pamphlet Der Bankrott des russischen Staatskommunismus (The Bankruptcy of Russian State Communism) attacking the Soviet Union. He denounced what he considered a massive oppression of individual freedoms and the suppression of anarchists starting with the purge on April 12, 1918. He supported instead the workers who took part in the Kronstadt uprising and the peasant movement led by the anarchist Nestor Makhno, whom he would meet in Berlin in 1923. In 1924, Rocker published a biography of Johann Most called Das Leben eines Rebellen (The Life of a Rebel). There are great similarities between the men's vitas. It was Rocker who convinced the anarchist historian Max Nettlau to start publication of his anthology Geschichte der Anarchie (History of Anarchy) in 1925.

During the mid 1920s, the decline of Germany's syndicalist movement started. The FAUD had reached its peak of around 150,000 members in 1921, but then started losing members to both the Communist and the Social Democratic Party. Rocker attributed this loss of membership to the mentality of German workers accustomed to military discipline, accusing the communists of using similar tactics to the Nazis and thus attracting such workers. At first only planning a short book on nationalism, he started work on Nationalism and Culture, which would be published in 1937 and become one of Rocker's best-known works, around 1925. 1925 also saw Rocker visit North America on a lecture tour with a total of 162 appearances. He was encouraged by the anarcho-syndicalist movement he found in the US and Canada.

Returning to Germany in May 1926, he became increasingly worried about the rise of nationalism and fascism. He wrote to Nettlau in 1927: "Every nationalism begins with a Mazzini, but in its shadow there lurks a Mussolini". In 1929, Rocker was a co-founder of the Gilde freiheitlicher Bücherfreunde (Guild of Libertarian Bibliophiles), a publishing house which would release works by Alexander Berkman, William Godwin, Erich Mühsam, and John Henry Mackay. In the same year he went on a lecture tour in Scandinavia and was impressed by the anarcho-syndicalists there. Upon return, he wondered whether Germans were even capable of anarchist thought. In the 1930 elections, the Nazi Party received 18.3% of all votes, a total of 6 million. Rocker was worried: "Once the Nazis get to power, we'll all go the way of Landauer and Eisner" (who were killed by reactionaries in the course of the Munich Soviet Republic uprising).

In 1931, Rocker attended the IWA congress in Madrid and then the unveiling of the Nieuwenhuis memorial in Amsterdam. In 1933, the Nazis came to power. After the Reichstag fire on February 27, Rocker and Witkop decided to leave Germany. As they left they received news of Erich Mühsam's arrest. After his death in July 1934, Rocker would write a pamphlet called Der Leidensweg Erich Mühsams (The Life and Suffering of Erich Mühsam) about the anarchist's fate. Rocker reached Basel, Switzerland, on March 8 by the last train to cross the border without being searched. Two weeks later, Rocker and his wife joined Emma Goldman in St. Tropez, France. There he wrote Der Weg ins Dritte Reich (The Path to the Third Reich) about the events in Germany, but it would only be published in Spanish.

In May, Rocker and Witkop moved back to London. There Rocker was welcomed by many of the Jewish anarchists he had lived and fought alongside for many years. He held lectures all over the city. In July, he attended an extraordinary IWA meeting in Paris, which decided to smuggle its organ Die Internationale into Nazi Germany.

On August 27, Rocker with his wife emigrated to New York. There they were reunited with Fermin who had stayed there after accompanying his father on his 1929 lecture tour in the US. The Rocker family moved to live with a sister of Witkop's in Towanda, Pennsylvania, where many families with progressive or libertarian socialist views lived. In October, Rocker toured the US and Canada speaking about racism, fascism, dictatorship, socialism in English, Yiddish, and German. He found many of his Jewish comrades from London, who had since emigrated to America, and became a regular writer for Freie Arbeiter Stimme, a Jewish anarchist newspaper. Back in Towanda in the Summer of 1934, Rocker started work on an autobiography, but news of Erich Mühsam's death led him to halt his work. He was working on Nationalism and Culture, when the Spanish Civil War broke out in July 1936 instilling great optimism in Rocker. He published a pamphlet The Truth about Spain and contributed to The Spanish Revolution, a special fortnightly newspaper published by American anarchists to report on the events in Spain. In 1937, he wrote The Tragedy of Spain, which analyzed the events in greater detail. In September 1937, Rocker and Witkop moved to the libertarian commune Mohegan Colony about 50 miles (80 km) from New York City.

In 1937, Nationalism and Culture, which he had started work on around 1925, was finally published with the help of anarchists from Chicago Rocker had met in 1933. A Spanish edition was released in three volumes in Barcelona, the stronghold of the Spanish anarchists. It would be his best-known work. In the book, Rocker traces the origins of the state back to religion claiming "that all politics is in the last instance religion": both enslave their very creator, man; both claim to be the source of cultural progress. He aims to prove the claim that culture and power are essentially antagonistic concepts. He applies this model to human history, analyzing the Middle Ages, the Renaissance, Enlightenment, and modern capitalist society, and to the history of the socialist movement. He concludes by advocating a "new humanitarian socialism".

In 1938, Rocker published a history of anarchist thought, which he traced all the way back to ancient times, under the name Anarcho-Syndicalism. A modified version of the essay would be published in the Philosophical Library series European Ideologies under the name Anarchism and Anarcho-Syndicalism in 1949.

In 1939, Rocker had to undergo a serious operation and was forced to give up lecture tours. However, in the same year, the Rocker Publications Committee was formed by anarchists in Los Angeles to translate and publish Rockers writings. Many of his friends died around this time: Alexander Berkman in 1936, Emma Goldman in 1940, Max Nettlau in 1944; many more were imprisoned in Nazi concentration camps. Although Rocker had opposed his teacher Kropotkin for his support of the Allies during World War I, Rocker argued that the Allied effort in World War II was just, as it would ultimately lead to preservation of libertarian values. Although he viewed every state as a coercive apparatus designed to secure the economic exploitation of the masses, he defended democratic freedoms, which he considered a result of a desire for freedom of the enlightened public. This position was criticized by many American anarchists, who did not support any war.

After World War II, an appeal in the Fraye Arbeter Shtime detailing the plight of German anarchists and called for Americans to support them. By February 1946, the sending of aid parcels to anarchists in Germany was a large-scale operation. In 1947, Rocker published Zur Betrachting der Lage in Deutschland (Regarding the Portrayal of the Situation in Germany) about the impossibility of another anarchist movement in Germany. It became the first post-World War II anarchist writing to be distributed in Germany. Rocker thought young Germans were all either totally cynical or inclined to fascism and awaited a new generation to grow up before anarchism could bloom once again in the country. Nevertheless, the Federation of Libertarian Socialists (FFS) was founded in 1947 by former FAUD members. Rocker wrote for its organ, Die Freie Gesellschaft, which survived until 1953. In 1949, Rocker published another well-known work. In Pioneers of American Freedom, a series of essays, he details the history of liberal and anarchist thought in the United States, seeking to debunk the idea that radical thought was foreign to American history and culture and had merely been imported by immigrants. On his eightieth birthday in 1953, a dinner was held in London to honor Rocker. Messages of gratitude were read by the likes of Thomas Mann, Albert Einstein, Herbert Read, and Bertrand Russell.

On September 10, 1958, Rocker died in the Mohigan Colony.