Claude McKay (1890-1948) is best known as a major figure of the Harlem Renaissance and a pioneer of Caribbean literature. He is less well known as a political thinker and activist. This thesis undertakes three tasks. First, it provides a detailed presentation of Claude McKay's political ideas and practices over time. Second, it critically engages with these. And finally, in the process, debunks and challenges a number of pervasive misconceptions of McKayfs politics. Although the analysis covers the period 1890 to 1920, it nevertheless is based upon the entire corpus of McKay's work - published and unpublished - from his early writings in Jamaica to those up to his death in 1948. His preoccupations and thought are placed within their historical context. The thesis thus draws upon his non-fiction texts, poetry, novels, short stories, journalism, unfinished manuscripts and correspondence. In the process, it demonstrates that McKay was a major political thinker, that his ideas have remarkable resonance today, especially in the United States, and that they are still relevant to contemporary black politics, particularly to those of the African diaspora. All in all, the thesis is a contribution to a better understanding of a remarkable man and outstanding figure of the African diaspora.