Daniel Steven Kowalski (born 2 July 1975 in Singapore) is a former Australian middle- and long-distance swimmer specialising in freestyle events. He competed in the Olympic Games in 200 m, 400 m and 1,500 m individual freestyle events and in the 4x200 m freestyle relay. At the 1996 Summer Olympics, he was the first man in 92 years to earn medals in all of the 200 m, 400 m and 1500 m freestyle events. Kowalski was however perhaps best known for being perpetual "groomsman" to fellow Australians Kieren Perkins and Grant Hackett, who were respectively the world's best 1500 m freestyle competitors during the earlier and later parts of Kowalski's career. He was an Australian Institute of Sport scholarship holder.
Won a swimming silver medal for Australia in the men's 1500 metre freestyle at the 1996 Olympic Games in Atlanta when he finished behind Kieren Perkins.