Born in 1818, he was the eldest son of Nicholas I of Russia and Charlotte of Prussia, daughter of Frederick William III of Prussia and Louise of Mecklenburg-Strelitz. His early life gave little indication of his ultimate potential; until the time of his accession in 1855, aged 37, few imagined that he would be known to posterity as a leader able to implement the most challenging reforms undertaken in Russia since the reign of Peter the Great. In the period of his life as heir apparent, the intellectual atmosphere of St. Petersburg was unfavourable to any kind of changes, freedom of thought and all private initiative being, as far as possible, suppressed vigorously. Personal and official censorship was rife; criticism of the authorities was regarded as a serious offence. Some 26 years after he had the opportunity of implementing changes he would, however, be assassinated in public by the Narodnaya Volya terrorist organisation.

His education as a future Tsar was carried out under the supervision of the liberal romantic poet and gifted translator Vasily Zhukovsky, grasping a smattering of a great many subjects, and becoming familiar with the chief modern European languages. His alleged lack of interest in military affairs detected by later historians could have been only his reflection on the results on his own family and on the effect on the whole country of the unsavoury Crimean War. Unusually for the time, the young Alexander was taken on a six-month tour of Russia, visiting 20 provinces in the country. He also visited many prominent Western European countries.

Alexander II succeeded to the throne upon the death of his father in 1855. The first year of his reign was devoted to the prosecution of the Crimean War and, after the fall of Sevastopol, to negotiations for peace, led by his trusted counsellor Prince Gorchakov. It was widely thought that the country had been exhausted and humiliated by the war. Encouraged by public opinion he began a period of radical reforms, including an attempt not to depend on a landed aristocracy controlling the poor, a move to developing Russia's natural resources and to thoroughly reform all branches of the administration.
After Alexander became tsar in 1855, he maintained a generally liberal course. Despite this he was a target for numerous assassination attempts (1866, 1879, 1880). On March 13 [O.S. March 1] 1881 members of the Narodnaya Volya (People's Will) party killed him with a bomb. The tsar had earlier in the day signed the Loris-Melikov constitution which would have created two legislative commissions made up of indirectly elected representatives, had it not been repealed by his reactionary successor Alexander III. In spite of his obstinancy in playing the Russian autocrat, Alexander II acted for several years somewhat like a constitutional sovereign of the continental type. Soon after the conclusion of peace, important changes were made in legislation concerning industry and commerce, and the new freedom thus afforded produced a large number of limited liability companies. Plans were formed for building a great network of railways—partly for the purpose of developing the natural resources of the country, and partly for the purpose of increasing its power for defence and attack.

The existence of serfdom was tackled boldly, taking advantage of a petition presented by the Polish landed proprietors of the Lithuanian provinces and, hoping that their relations with the serfs might be regulated in a more satisfactory way (meaning in a way more satisfactory for the proprietors), he authorised the formation of committees "for ameliorating the condition of the peasants", and laid down the principles on which the amelioration was to be effected. This step was followed by one still more significant. Without consulting his ordinary advisers, Alexander ordered the Minister of the Interior to send a circular to the provincial governors of European Russia, containing a copy of the instructions forwarded to the governor-general of Lithuania, praising the supposed generous, patriotic intentions of the Lithuanian landed proprietors, and suggesting that perhaps the landed proprietors of other provinces might express a similar desire. The hint was taken: in all provinces where serfdom existed, emancipation committees were formed. But the emancipation was not merely a humanitarian question capable of being solved instantaneously by imperial ukase. It contained very complicated problems, deeply affecting the economic, social and political future of the nation. Alexander had to choose between the different measures recommended to him. Should the serfs become agricultural labourers dependent economically and administratively on the landlords, or should they be transformed into a class of independent communal proprietors? The emperor gave his support to the latter project, and the Russian peasantry became one of the last groups of peasants in Europe to shake off serfdom. The architects of the emancipation manifesto were Alexander's brother Konstantin, Yakov Rostovtsev, and Nikolay Milyutin. On 3 March 1861, 6 years after his accession, the emancipation law was signed and published.

Army and navy reorganisation and rearmament was initiated in response to the overwhelming defeat suffered by Russia in the Crimean War, and an awareness of military advances being implemented in other European countries. The changes included universal military conscription, the creation of an army reserve and the military district system (still in use a century later), the building of strategic railways, and an emphasis on the military education of the officer corps.

A new judicial administration based on the French model (1864); a new penal code and a greatly simplified system of civil and criminal procedure.

An elaborate scheme of local self-government (Zemstvo) for the rural districts (1864) and the large towns (1870), with elective assemblies possessing a restricted right of taxation, and a new rural and municipal police under the direction of the Minister of the Interior were instituted.

During his bachelor days, Alexander made a state visit to England in 1838. Just a year older than the young Queen Victoria, Alexander's approaches to her were indeed short-lived. Victoria married her German cousin, Prince Albert of Saxe-Coburg in February 1840. On 16 April 1841, aged 23, Tsarevitch Alexander married Princess Marie of Hesse in St Petersburg, thereafter known in Russia as Maria Alexandrovna. (Marie was the legal daughter of Ludwig II, Grand Duke of Hesse and by Rhine and Princess Wilhelmina of Baden, although some gossiping questioned whether the Grand Duke Ludwig or Wilhelmina's lover, Baron August von Senarclens de Grancy, was her biological father. Alexander was aware of the question of her paternity). The marriage produced six sons and two daughters. Alexander had many mistresses during his marriage and fathered 7 known illegitimate children. On 6 July 1880, less than a month after Tsarina Maria's death on 8 June, Alexander formed a morganatic marriage with his mistress Princess Catherine Dolgorukov, with whom he already had four children.

At the beginning of his reign, Alexander expressed the famous statement "No dreams" addressed to the Poles who inhabited Congress Poland, Western Ukraine, Lithuania, Livonia and Belarus. The result was the January Uprising of 1863–1864 that was suppressed after eighteen months of fighting. Hundreds of Poles were executed, and thousands were deported to Siberia. The price for suppression was Russian support for Prussian-united Germany. Twenty years later, Germany became the major enemy of Russia on the continent. All territories of the former Poland-Lithuania were excluded from liberal policies introduced by Alexander. The martial law in Lithuania, introduced in 1863, lasted for the next 40 years. Native languages, Lithuanian, Ukrainian and Belarusian were completely banned from printed texts. The Polish language was banned in both oral and written form from all provinces except Congress Poland, where it was allowed in private conversations only.

In 1863 Alexander II re-established the Diet of Finland and initiated several reforms increasing Finland's autonomy from Russia including establishment of its own currency, the Markka. Liberation of business led to increased foreign investment and industrial development. Finally, the elevation of Finnish from a language of the common people to a national language equal to Swedish opened opportunities for a larger proportion of the society. Alexander II is still regarded as "The Good Tsar" in Finland. These reforms could be seen as results of a genuine belief that reforms were easier to test in an underpopulated, homogeneous country, than in the whole of Russia. They may also be seen as a reward for the loyalty of its relatively western-oriented population during the Crimean war and during the Polish uprising. Encouraging Finnish nationalism and language can also be seen as an attempt to dilute ties with Sweden.

In 1866, there was an attempt on the tsar's life in St. Petersburg by Dmitry Karakozov. To commemorate his narrow escape from death (which he himself referred to only as "the event of 4 April 1866"), a number of churches and chapels were built in many Russian cities. Viktor Hartmann, a Russian architect, even sketched a design of a monumental gate (planned, never built) to commemorate the event. Modest Mussorgsky later wrote his Pictures at an Exhibition; the last movement of which, "The Great Gate of Kiev", is based on Hartmann's sketches. On the morning of 20 April 1879, Alexander II was briskly walking towards the Square of the Guards Staff and faced Alexander Soloviev, a 33-year-old former student. Having seen a menacing revolver in his hands, the Tsar fled. Soloviev fired five times but missed, and was sentenced to death and hanged on 28 May. The student acted on his own, but other revolutionaries were keen to murder Alexander. In December 1879, the Narodnaya Volya (People's Will), a radical revolutionary group which hoped to ignite a social revolution, organized an explosion on the railway from Livadia to Moscow, but they missed the tsar's train. On the evening of 5 February 1880 Stephan Khalturin, also from Narodnaya Volya, set off a charge under the dining room of the Winter Palace, right in the resting room of the guards a story below. Being late for dinner, the tsar was unharmed; although 11 other people were killed and 30 wounded. After the last assassination attempt in February 1880, Count Loris-Melikov was appointed the head of the Supreme Executive Commission and given extraordinary powers to fight the revolutionaries. Loris-Melikov's proposals called for some form of parliamentary body, and the Emperor seemed to agree; these plans were never realised.

On 13 March (1 March Old Style Date), 1881, Alexander fell victim to an assassination plot. As he was known to do every Sunday for many years, the tsar went to the Manezh to review the Life Guards. He travelled both to and from the Manezh in a closed carriage accompanied by six Cossacks with a seventh sitting on the coachman's left. The tsar's carriage was followed by two sleighs carrying, among others, the chief of police and the chief of the tsar's guards. The route, as always, was via the Catherine Canal and over the Pevchesky Bridge. The street was flanked by narrow sidewalks for the public. A young member of the Narodnaya Volya (People's Will) movement, Nikolai Rysakov, was carrying a small white package wrapped in a handkerchief. The explosion, while killing one of the Cossacks and seriously wounding the driver and people on the sidewalk, had only damaged the bulletproof carriage, a gift from Napoleon III of France. The tsar emerged shaken but unhurt. Rysakov was captured almost immediately. Police Chief Dvorzhitsky heard Rysakov shout out to someone else in the gathering crowd. The surrounding guards and the Cossacks urged the tsar to leave the area at once rather than being shown the site of the explosion. A second young member of the Narodnaya Volya, Ignacy Hryniewiecki, standing by the canal fence, raised both arms and threw something at the tsar's feet. He was alleged to have shouted, "It is too early to thank God". Dvorzhitsky was later to write:

"I was deafened by the new explosion, burned, wounded and thrown to the ground. Suddenly, amid the smoke and snowy fog, I heard His Majesty's weak voice cry, 'Help!' Gathering what strength I had, I jumped up and rushed to the tsar. His Majesty was half-lying, half-sitting, leaning on his right arm. Thinking he was merely wounded heavily, I tried to lift him but the tsar's legs were shattered, and the blood poured out of them. Twenty people, with wounds of varying degree, lay on the sidewalk and on the street. Some managed to stand, others to crawl, still others tried to get out from beneath bodies that had fallen on them. Through the snow, debris, and blood you could see fragments of clothing, epaulets, sabers, and bloody chunks of human flesh."

Later it was learned there was a third bomber in the crowd. Ivan Emelyanov stood ready, clutching a briefcase containing a bomb that would be used if the other two bombers failed.

Alexander was carried by sleigh to the Winter Palace to his study where ironically, twenty years before almost to the day, he had signed the Emancipation Edict freeing the serfs. Alexander was bleeding to death, with his legs torn away, his stomach ripped open, and his face mutilated. Members of the Romanov family came rushing to the scene. The dying tsar was given Communion and Extreme Unction. When the attending physician, Dr. S. P. Botkin, was asked how long it would be, he replied "Up to fifteen minutes" At 3:30 that day the standard of Alexander II was lowered for the last time.

The assassination caused a great setback for the reform movement. One of Alexander II's last ideas was to draft plans for an elected parliament, or Duma, which were completed the day before he died but not yet released to the Russian people. The first action Alexander III took after his coronation was to tear up those plans. A Duma would not come into fruition until 1905, when Alexander II's grandson, Nicholas II, commissioned the Duma following extreme pressure on the monarchy as a result of the Russian Revolution of 1905. A second consequence of the assassination was anti-Jewish pogroms and legislation. A third consequence of the assassination was that suppression of civil liberties in Russia and police brutality burst back in full force after experiencing some restraint under the reign of Alexander II. Alexander II's murder and subsequent death was witnessed first-hand by his son, Alexander III, and his grandson, Nicholas II, both future Tsars, who vowed not to have the same fate befall them. Both used the Okhrana to arrest protestors and uproot suspected rebel groups, creating further suppression of personal freedom for the Russian people.