Mark Webster Chatfield (August 11, 1953 – December 23, 1998) was an American breaststroke swimmer and breaststroke specialist. Chatfield won the gold medal in the 100-meter breaststroke at the 1971 Pan American Games. He represented the United States as a 19-year-old at the 1972 Summer Olympics in Munich, Germany. He advanced to the event final of the men's 100-meter breaststroke, finishing fourth with a time of 1:06.1. An accomplished Baroque and period musician, vocalist and composer, he played cello and was a countertenor. Chatfield died of lymphoma on December 23, 1998; he was 45 years old.