Gretha Smit (born January 20, 1976 in Rouveen) is a Dutch speed skater.

Smit won a surprising silver medal in the 2002 Winter Olympics in the 5000 meter event. Prior to that season, she had not competed in long track speed skating competitions for several years, and had only taken up practice again shortly before the Dutch trials in late 2001.

However, she had been a very successful marathon skater in the years before 2002. She had become Dutch marathon skating champion on natural ice in 1995, 1998, 2000 and 2001, and on artificial ice in 1999, 2000 and 2001. During the last held Elfstedentocht in 1997 she finished second. She also won the alternative Elfstedentocht - skated in Finland - in 1998, 2000 and 2001.

Smit's two sisters, Jenita and Marianne, were also good (marathon) skaters; Jenita also took up long track skating in the 2002/2003 season.