This chapter situates the emerging antifascism of Diego Rivera and other Mexican artists within the broader contexts of post-revolutionary Mexico, the rise of global fascism, and shifts of the global left. Their antifascism emerged slowly in the 1920s, subordinate to their sharp anti-capitalism and anti-imperialism, but moved to the forefront from the mid-30s with the rise of Hitler, the Spanish Civil War, and as part of Popular Front strategies across the progressive left. Rivera’s antifascism, shaped by his Communist dissidence during the 1930s, most fully emerged in his US murals. His Portrait of America (1933) denounces US capitalism and imperialism, while addressing the urgency of proletarian unity against fascism. Pan American Unity (1940) reflects Rivera’s disgust with the Nazi-Soviet Non-Aggression Pact of 1939. It proposes a cultural and political alliance between Latin America and the once-imperial US as the only way to defeat the alliance of Nazi and Soviet totalitarianisms.