Yvonne Vermaak
Yvonne Vermaak is a former tour tennis player who represented her native South Africa.
Vermaak's best result was reaching the semi-finals of the 1983 Wimbledon Championships, defeating Virginia Wade in the quarter-finals.
In 1977 she won the All England Plate, a competition for players who were defeated in the first and second rounds of the Wimbledon singles competition. In the final she defeated Sue Mappin in straight sets.
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.
Career finals
Singles 6 (4–2)
Doubles 7 (4–3)
| Result | No. | Date | Tournament | Surface | Partner | Opponents | Score |
| Loss | 1. | 16 June 1978 | Chichester, England | Grass |  Michelle Tyler |  Janet Wright Pam Shriver | 6–3, 3–6, 4–6 |
| Loss | 2. | 19 July 1981 | Kitzbühel, Austria | Clay |  Elizabeth Little |  Claudia Kohde-Kilsch Eva Pfaff | 4–6, 3–6 |
| Win | 3. | 9 May 1982 | Perugia, Italy | Clay | Kathy Horvath | Billie Jean King  Ilana Kloss | 2–6, 6–4, 7–6 |
| Loss | 4. | 6 November 1982 | Hong Kong | Clay | Jennifer Mundel | Laura duPont Alycia Moulton | 2–6, 6–4, 5–7 |
| Win | 5. | 19 September 1983 | Salt Lake City, Utah, USA | Hard |  Cláudia Monteiro | Amanda Brown Brenda Remilton | 6–1, 3–6, 6–4 |
| Win | 6. | 5 February 1984 | Indianapolis, Indiana, USA | Hard | Cláudia Monteiro | Beverly Mould Elizabeth Sayers | 6–7, 6–4, 7–5 |
| Win | 7. | 6 April 1984 | Miami, Florida, USA | Clay | Patricia Medrado | Kate Latham Janet Wright | 6–3, 6–3 |