Helen Elizabeth "Betsy" Nagelsen McCormack (born October 23, 1956) is an American former professional tennis player.

She had career wins over Navratilova, Arantxa Sánchez Vicario, Sue Barker, Pam Shriver, Claudia Kohde-Kilsch, Rosie Casals, Betty Stöve, and Sylvia Hanika.

After her retirement in 1996, Nagelsen became a commentator for ABC and ESPN in the United States and Australia's Nine Network.

She married Mark McCormack, founder of the sports management group IMG.

The couple donated money for the McCormack-Nagelsen Tennis Center at the College of William and Mary in Williamsburg, Virginia.