Riley Marie Gaines (born April 21, 2000), also known as Riley Gaines Barker, is an American political activist and swimmer, known for campaigning against the participation of trans women in women's sports. As a 12-time NCAA All-American, she competed for the University of Kentucky NCAA swim team before retiring from competition and focusing on political activism.

Since 2023, she has hosted the weekly OutKick and Fox Nation podcast Gaines for Girls.