Steffi Graf is a tennis player.
Steffi Graf . Graf was ranked world No. 1 by the Women 's Tennis Association ( WTA ) for a record 377 total weeks -- the longest period for which any player , male or female , has held the number-one ranking since the WTA and the Association of Tennis Professionals began issuing rankings . In 1999 Billie Jean King said `` Steffi is definitely the greatest women 's tennis player of all time '' .