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.
He won the silver medal at the 2016 Olympic Games in Rio at the 10 km marathon swim. Initially Gianniotis was given as the gold medalist as he appeared to cross the finish line first, but the Dutchman Ferry Weertman touched the timing pad before him. After 15 minutes of deliberations by the judges and the use of photo finish, Weertman was awarded the gold medal and Gianniotis the silver, despite the fact that both were credited with the same time: 1 hour, 52 minutes, 59.8 seconds (1:52:59.8). Gianniotis won the silver medal at the age of 36, being the oldest competitor in the event.