12. Louise Brough Clapp (4)
The USA’s Louise Brough Clapp won a ridiculous 21 Grand Slam doubles titles in her career from 1942 to 1957. And while she wasn’t quite as dominant all by herself, she did pretty well. She won the U.S. Open Singles Title in 1947 and the Australian Open Singles Title in 1950, plus Wimbledon in 1948, 1949, 1950, and 1955.