Yvonne Vermaak is a former tour tennis player who represented her native South Africa.
Vermaak's best result was defeating Virginia Wade in the quarter-finals of the 1983 Wimbledon Championships.
Late in her playing career, Vermaak became an American citizen.
Vermaak played USTA Master's tennis. Representing Illinois, she was the 1992 Singles Champion of the USTA National Women's Indoor Championships in Homewood for 35's. In 1993, Yvonne Vermaak was the 25's Singles Champion, and again she was the 25's Singles Champion in 1994. In 1995, Vermaak moved on to Doubles, winning the 25's and 35's doubles with her partner Ann Kiyomura-Hayashi of California. The 1995 Championships was Vermaak's last USTA Championships win.