Swimming at the 11th Pan American Games was held August 12–18, 1991 in Havana, Cuba. The competition consisted of 32 events (26 individual and 6 relay); and were contested in the long course (50m) pool. Brazil's victory in the men's 4x100m freestyle relay was only the second time that the U.S. lost the gold in a relay event, at the Pan American Games. The first had been to Canada in women's 4x100m medley at the 1971 Pan American Games.