Harry Haywood (February 4, 1898 – January 4, 1985) was an American political activist and a leading figure in the Communist Party of the United States (CPUSA). He was principally known for his efforts "to bring the political philosophy of the Party in line with issues of race."

In 1926, he joined with other African-American communists and traveled to the Soviet Union as a student. While there he became a Communist International (Comintern) delegate. He stayed four years and studied the Marxist-Leninist theory of the "national question" regarding how to unify ethnic nationalities within a country's dominant culture. Haywood's work in the USSR resulted in his being selected to head the CPUSA's "Negro Department". In the 1930s he organized a movement to defend the Scottsboro boys in Alabama. He made theoretical contributions to the African-American national question. He argued that blacks represented an oppressed nation inside the U.S. and had the right to self-determination. His doctrine was known as the Black Belt thesis, i.e., blacks should be able to form their own nation-state in the Black Belt South. In the 1950s as the CPUSA platform moved away from black nationalism and separatism and towards integration, Haywood lost standing in the Party until he was expelled in 1959.

Haywood fought in three wars: World War I, the Spanish Civil War, and World War II. He authored several books and pamphlets, including Negro Liberation in 1948, and "For a Revolutionary Position on the Negro Question" in 1957. After his expulsion from the CPUSA, he remained a left-wing activist. In the 1960s, he became involved in the Maoist New Communist movement. In 1978, his autobiography Black Bolshevik was published.

Harry Haywood was born Haywood Hall Jr., on February 4, 1898, in South Omaha, Nebraska, to former slaves Harriet and Haywood Hall, from Missouri and West Tennessee, respectively. They had migrated to Omaha because of jobs with the railroads and meatpacking industry, as did numerous other Southern blacks. South Omaha also attracted white immigrants, and ethnic Irish had established an early neighborhood there. Haywood was the youngest of three sons.

In 1913 after Haywood Hall Sr. was attacked by whites, the Hall family moved to Minneapolis, Minnesota. Two years later in 1915 they moved to Chicago. The younger Hall's education was limited. He never went beyond the eighth grade and had to self-educate afterward. At age sixteen, he began working as a dining car waiter on the Chicago and North Western Railway line.

During World War I, he served with the Eighth Regiment, a black U.S. regiment. Upon his return to Chicago, he was radicalized by the bitter Red Summer of 1919, especially the Chicago race riot, in which mostly ethnic Irish attacked blacks on the South Side. Hall was influenced by his older brother Otto, who joined the Communist Party in 1921 and invited him to enter the secret African Blood Brotherhood. Hall was also affected by his reading of Vladimir Lenin's State and Revolution. He later wrote in his autobiography that "this work was the single most important book I had read in the entire three years of my political search and was decisive in leading me to the Communist Party."

Hall's military career included service in three wars. His interest in military combat began when his friends told tales of heroic feats by the Eighth Illinois, a Black National Guard Regiment. In WWI, he saw action in the Soissons sector of France in the summer of 1918. In the Spanish Civil War, he fought for the Popular Front with the Abraham Lincoln Battalion of the International Brigades. He held the position of Regimental Commissar in the XV International Brigade during the Battle of Brunete. While in Spain he, Langston Hughes and Walter Benjamin Garland broadcast from Madrid in support of the Republican cause. During World War II, Haywood was involved with the National Maritime Union in San Pedro, California. This led to his enlisting in 1943 in the U.S. Merchant Marines.

Hall began his revolutionary career by joining the African Blood Brotherhood in 1922, followed by the Young Communist League in 1923. Two years later he joined the Communist Party, USA (CPUSA), recruited by Robert Minor. Soon thereafter, Hall was sent to Moscow to "train as a revolutionary". At the time, he and his CPUSA friends believed they were targets of FBI scrutiny. When he applied for a passport, he chose to use an alias, "Harry Haywood". He said it was derived from his mother's first name (Harriet) and father's first name (Haywood), and that it would "stick with me the rest of my life."