Most nationalities require a ‘tour card’ to visit Cuba. This is issued instead of a visa and must be obtained from the Cuban embassy or consulate in your home country. Some airlines allow you to buy a tour card at the airport when you depart from home, but please check with your airline for more information.
American citizens, permanent residents and visa holders are subject to special rules. Please refer to the US Department of State Bureau of Consular Affairs website - travel.state.gov - for the latest advice.