Spyridon "Spyros" Gianniotis (; born 19 February 1980) is a Greek competitive swimmer who specialises in long-distance and open-water freestyle events. He is an Olympic silver medalist, two-time World Champion, World Cup gold medalist, and two-time European Champion. A five-time Olympian, Gianniotis has won a total of 15 medals in major international long-course competition, totalling 5 gold, 5 silver, and 5 bronze spanning the Olympics, the World Championships, the World Cup and the European Championships. In 2011 he won the World Open Water Swimmer of the Year award, becoming the first and only Greek swimmer to earn that distinction.