Alexander "Alex" Trachtenberg (November 23, 1884 – December 26, 1966) was an American publisher of radical political books and pamphlets, founder and manager of International Publishers of New York. He was a longtime activist in the Socialist Party of America and later in the Communist Party USA. For more than eight decades, his International Publishers was a part of the publishing arm of the American communist movement. He served as a member of the CPUSA's Central Control Committee. During the period of McCarthyism in America, Trachtenberg was twice subject to prosecution and convicted under the Smith Act; the convictions were overturned, the first by recanting of a government witness and the second by a US Circuit Court of Appeals decision in 1958.

Alexander Leo Trachtenberg, later known to his friends as "Alex" or "Trachty," was born on November 23, 1885, of Jewish parents in the city of Odesa, part of the Pale of Settlement of the Russian Empire.

Trachtenberg joined the radical movement while attending the University of Odessa School of Electrotechnique as an engineering student from 1902 to 1904. During the Russo-Japanese War, he was conscripted into the Russian army. For his service, he earned the Cross of the Order of St. George and rose to the rank of captain.

Soon after his return home in the late summer of 1905, Trachtenberg was arrested and imprisoned by the government for a year, during a period of political dissidents suppression. During the Russian Revolution of 1905, Trachtenberg escaped pogroms against the Jews in 1905 and 1906. Soon after his release in 1906, he joined many other Jews in political emigration to the United States.

Trachtenberg arrived in New York City on August 6, 1906, on a ship from Hamburg, Germany, a major port of departure to the US. From 1908 to 1915, Trachtenberg was a student at three different universities, earning his bachelor's degree from Trinity College in Hartford, Connecticut, in 1911, followed by a master's degree in education from Yale University in 1912. He continued studies in economics at Yale through 1915 and completed a dissertation on safety legislation for the protection of Pennsylvania coal miners, but he did not complete his doctorate. Trachtenberg's dissertation was accepted for publication by the United States Department of Labor in 1917, but delays in preparation of the manuscript and budgetary issues at the department ultimately ended the project. Trachtenberg finally published his manuscript a quarter of a century later through International Publishers, which he co-founded, as The History of Legislation for the Protection of Coal Miners in Pennsylvania, 1824–1915.

Trachtenberg was very active in student affairs, serving as president of the Yale chapter of the Intercollegiate Socialist Society (ISS). During World War I, he took an anti-militarist stance from a socialist rather than a pacifist perspective. He joined the Collegiate Anti-Militarism League at Columbia University in 1915, served as treasurer, and contributed to an anti-war petition to President Wilson after the sinking of the Lusitania.

Trachtenberg left Yale in 1915 to work as an administrator and teacher of Economics and Labor at the Rand School of Social Science, founded by the Socialist Party in New York. Trachtenberg directed the school's Department of Labor Research, which conducted studies for other organizations and gathered and published labor statistics. He edited various Rand publications, including the first four volumes of the Rand School's encyclopedic American Labor Year Book, as well as a controversial 1917 defense of the Socialist Party's anti-militarist perspective, American Socialists and the War. Trachtenberg continued to oppose the war even after the United States entry into the conflict on the side of the Allies in April 1917.

In June 1920, the International Ladies Garment Workers Union (ILGWU) hired Trachtenberg as an economist.