Grant George Hackett OAM (born 9 May 1980) is a former Australian swimmer most famous for winning the men's 1500 metres freestyle race at both the 2000 Summer Olympics in Sydney and the 2004 Summer Olympics in Athens. This achievement has led him to be regarded as one of the greatest distance swimmers in history. He also collected a gold medal in Sydney for swimming in the heats of the 4×200 m freestyle relay. He is well regarded for his versatility, being the world record holder in the 1500 m and 800 m freestyle, and 2nd and 4th in the 400 m and 200 m freestyle respectively. He has dominated the 1500 m event in the past decade, being undefeated in the event in finals from 1996 until the 2007 World Aquatics Championships. His four World Championship gold medals in the event make him the only swimmer to have won a world title in one event four times, and in total, he has won 10 World Championship gold medals.

Hackett was the captain of the Australian swimming team since the role was reintroduced in 2005, until his retirement in 2008.

Hackett also presents sport on Nine News Melbourne on weekends. He is now working for Westpac as a banker and has expressed interest in a political career in the future.