Whose open-era record of 22 Grand Slams did Serena Williams overtake when she won the 2017 Australian Open?

Stefanie Maria "Steffi" Graf (born 14 June 1969) is a German former professional tennis player, who was ranked world No. 1 during her career. Graf won 22 Grand Slam singles titles. Her 22 singles titles put her second on the list of Major wins in the female competition since the introduction of the open-era in 1968.

On January 28, 2017, Williams won the Australian Open for an open-era record seventh time, defeating her sister, Venus. This was her 23rd Grand Slam singles title, surpassing Steffi Graf's open-era record of 22. It was the first time in the open-era that two players aged 35 or older competed in the final of a Grand Slam tournament. The win ensured her return to the No. 1 ranking.

Williams subsequently withdrew from the Indian Wells and Miami Opens, citing a knee injury. However, on April 19, 2017, she revealed that she was 20 weeks pregnant and would miss the remainder of the season. The timing means that she would have been roughly eight-weeks pregnant when she won the Australian Open. In interviews, she has maintained that she intends to return to tennis after her pregnancy, including setting (in her own words) the "outrageous plan" of competing in the 2018 Australian Open.