Eugene Victor Debs (November 5, 1855 – October 20, 1926) was an American union leader, one of the founding members of the International Labor Union and the Industrial Workers of the World (IWW), and several times the candidate of the Socialist Party of America for President of the United States. Through his presidential candidacies, as well as his work with labor movements, Debs eventually became one of the best known socialists living in the United States.

In the early part of his political career, Debs was a member of the Democratic Party. He was elected as a Democrat to the Indiana General Assembly in 1884. After working with several smaller unions, including the Brotherhood of Locomotive Firemen, Debs was instrumental in the founding of the American Railway Union (ARU), the nation's first industrial union. When the ARU struck the Pullman Palace Car Company over pay cuts, President Grover Cleveland used the United States Army to break the strike. As a leader of the ARU, Debs was later imprisoned for failing to obey an injunction against the strike. Debs educated himself about socialism in prison and emerged to launch his career as the nation's most prominent socialist in the first decades of the 20th century. He ran as the Socialist Party's candidate for the presidency in 1900, 1904, 1908, 1912, and 1920, the last time from his prison cell. Noted for his oratory, it was a speech denouncing American participation in World War I that led to his second arrest in 1918. He was convicted under the Espionage Act of 1917 and sentenced to a term of 10 years. President Warren G. Harding commuted his sentence in December 1921. Debs died in 1926 not long after being admitted to a sanatorium.

Eugene Debs was born on November 5, 1855, in Terre Haute, Indiana, to Jean Daniel and Marguerite Marie Bettrich Debs, who both immigrated to the United States from Colmar, Alsace, France. His father, who was born to a prosperous family in France, owned a textile mill and meat market. Eugene Victor Debs was named after the French authors Eugene Sue and Victor Hugo.

Debs dropped out of high school at age 14 to work as a paint scraper in railroad yards. In 1870, he became a boilerman. During his time as a boilerman, he attended a local business school during the night. He returned home in 1874 to work as a grocery clerk. The next year he became a founding member and secretary of a new lodge of the Brotherhood of Locomotive Firemen. He rose quickly in the Brotherhood, becoming first an assistant editor for their magazine and then the editor and Grand Secretary in 1880. At the same time, he became a prominent figure in the community; in 1884 he was elected to the Indiana General Assembly as a Democrat, serving for one term.

The railroad brotherhoods were comparatively conservative unions, more focused on providing fellowship and services than in collective bargaining. Debs gradually became convinced of the need for a more unified and confrontational approach. After stepping down as Brotherhood Grand Secretary in 1893, he organized one of the first industrial unions in the United States, the American Railway Union (ARU). The Union successfully struck the Great Northern Railway in April 1894, winning most of its demands.

Eugene Debs married Kate Metzel on June 9, 1885. The couple had no children. Their home still stands in Terre Haute, within Indiana State University.

In 1894 Debs became involved in the Pullman Strike, which grew out of a compensation dispute started by the workers who constructed the train cars made by the Pullman Palace Car Company. The Pullman Company, citing falling revenue after the economic Panic of 1893, had cut the wages of its employees by 28%. The workers, many of whom were already members of the American Railway Union, appealed for support to the union at its convention in Chicago, Illinois. Debs tried to persuade the Union members who worked on the railways that the boycott was too risky, given the hostility of both the railways and the federal government, the weakness of the Union, and the possibility that other unions would break the strike. The membership ignored his warnings and refused to handle Pullman cars or any other railroad cars attached to them, including cars containing U.S. Mail. After A.R.U. Board Director Martin J. Elliot extended the strike to St. Louis, doubling its size to 80.000 workers, Debs relented and decided to take part in the strike, which was now endorsed by almost all members of the ARU in the immediate area of Chicago. On July 9, 1894, a New York Times editorial called Debs "a lawbreaker at large, an enemy of the human race." Strikers fought by establishing boycotts of Pullman train cars, and with Debs' eventual leadership, the strike came to be known as "Debs' Rebellion".

The U.S. federal government intervened, obtaining an injunction against the strike on the theory that the strikers had obstructed the U.S. Mail, carried on Pullman cars, by refusing to show up for work. President Grover Cleveland sent the United States Army to enforce the injunction. The entrance of the Army was enough to break the strike; 13 strikers were killed, and thousands were blacklisted. An estimated $80 million worth of property was damaged, and Debs was found guilty of contempt of court for violating the injunction and sent to federal prison.

Debs was represented by Clarence Darrow, hitherto a corporate lawyer for the railroad company, who "switched sides" to represent Debs. Darrow, a leading American lawyer and civil libertarian, had resigned his corporate position in order to represent Debs, making a substantial financial sacrifice in order to do so. A Supreme Court case decision, In re Debs, later upheld the right of the federal government to issue the injunction.

At the time of his arrest for mail obstruction, Debs was not yet a socialist. While incarcerated in Woodstock, Illinois, he was mentored in Socialism by Martin J. Elliott, Director of the American Railway Union, leader of the St. Louis Pullman strike, and fellow prisoner who had brought along books on Socialism to read and share in jail. After Debs' release from prison in 1895, he started his Socialist political career. Debs persuaded the American Railway Union membership to join with the Brotherhood of the Cooperative Commonwealth to found the Social Democracy of America. Debs, along with Elliott, were the first federal office candidates for the fledgling Socialist party, running (unsuccessfully) for US president and Congress in 1900. Along with his running mate Job Harriman, Debs received 87,945 votes — 0.6% of the popular vote — and no electoral votes.

One year later this group split and Debs went with the majority faction to found the Socialist Democratic Party of the United States, also called the Social Democratic Party. Debs was elected chairman of the Executive Board of the National Council, the board which governed the party. Although the party did not have a sole figure that governed its actions, Debs' position as chairman and his notoriety gave him the status of party figurehead. He was the Socialist Party of America candidate for president in 1904, 1908, 1912, and 1920 (the final time from prison).

In his showing in the 1904 election, Debs received 402,810 votes, which was 2.98% of the popular vote. Debs received no electoral votes, and, with vice presidential candidate Benjamin Hanford, ultimately finished third overall. In the 1908 election, Debs again ran on the same ticket as Benjamin Hanford. While receiving a slightly higher number of votes in the popular vote, 420,852, he received 2.83% of the popular vote. Again Debs received no electoral votes. Debs received 5.99% of the popular vote (a total of 901,551 votes) in 1912, while his total of 913,693 votes in the 1920 campaign remains the all time high for a Socialist Party candidate. Running alongside Emil Seidel, Debs again received no electoral votes.

Although he received some success as a third party candidate, Debs was largely dismissive of the electoral process; he distrusted the political bargains that Victor Berger and other "Sewer Socialists" had made in winning local offices. He put much more value on organizing workers into unions, favoring unions that brought together all workers in a given industry over those organized by the craft skills workers practiced. Debs saw the working class as the one class to organize, educate, and emancipate itself by itself.

After his work with the Brotherhood of Locomotive Firemen and the American Railway Union, Debs' next major work in organizing a labor union came during the founding of the Industrial Workers of the World (IWW). On June 27, 1905, in Chicago, Illinois, Debs and other influential union leaders including Big Bill Haywood, leader of the Western Federation of Miners, and Daniel De León, leader of the Socialist Labor Party, held what Haywood called the "Continental Congress of the working class". Haywood stated: "We are here to confederate the workers of this country into a working class movement that shall have for its purpose the emancipation of the working class...", and for Debs: "We are here to perform a task so great that it appeals to our best thought, our united energies, and will enlist our most loyal support; a task in the presence of which weak men might falter and despair, but from which it is impossible to shrink without betraying the working class."

The Cooper Union speech was the beginning of a split between Bill Haywood and the Socialist Party, leading to the split between the factions of the IWW, one faction loyal to the Socialist Party, and the other to Haywood. The rift presented a problem for Debs, who was influential in both the IWW and the Socialist Party. The final straw between Haywood and the Socialist Party came during the Lawrence textile strike when, disgusted with the decision of the elected officials in Lawrence, Massachusetts, to send police who subsequently used their clubs on children, Haywood publicly declared that "I will not vote again" until such a circumstance was rectified. Haywood was purged from the National Executive Committee by passage of an amendment that focused on the direct action and sabotage tactics advocated by the IWW. Debs was probably the only person who could have saved Haywood's seat.

In 1906, when Haywood had been on trial for his life in Idaho, Debs had described him as "the Lincoln of Labor" and called for Haywood to run against Theodore Roosevelt for president of the United States, but times had changed and Debs, facing a split in the Party, chose to echo Hillquit's words, accusing the IWW of representing anarchy. Debs thereafter stated that he had opposed the amendment, but that once it was adopted it should be obeyed. Debs remained friendly to Haywood and the IWW after the expulsion, despite their perceived differences over IWW tactics.

Prior to Haywood's dismissal, the Socialist Party membership had reached an all time high of 135,000. One year later, four months after Haywood was recalled, the membership dropped to 80,000. The reformists in the Socialist Party attributed the decline to the departure of the "Haywood element", and predicted that the party would recover. It did not; in the election of 1912 many of the Socialists who had been elected to public office lost their seats.

Although sometimes called "King Debs", Debs himself was not wholly comfortable with his standing as a leader. As he told an audience in Utah in 1910:

I am not a Labor Leader; I do not want you to follow me or anyone else; if you are looking for a Moses to lead you out of this capitalist wilderness, you will stay right where you are. I would not lead you into the promised land if I could, because if I led you in, some one else would lead you out. You must use your heads as well as your hands, and get yourself out of your present condition.