Steffi Graf is an athlete.
The Grand Slam tournaments , also called majors , are the four most-important annual tennis events . Stefanie Maria `` Steffi '' Graf ( [ ˈʃtɛfiː ˈgʁa : f ] ; born 14 June 1969 ) is a German former tennis player , who was ranked world No. 1 during her career . Graf won 22 Grand Slam singles titles . Furthermore , she is the only tennis player to have won each Grand Slam event at least four times .