Madison Keys was the defending champion who lost in the fourth round of the 2026 Australian Open women’s singles tournament. Jessica Pegula defeated Keys 6–3, 6–4 in an all-American match at Melbourne Park.
Keys entered the event as the reigning champion after winning her first Grand Slam title at the 2025 Australian Open. Her 2025 breakthrough included victories over several highly ranked opponents and made her the player everyone else had to chase in the following tournament.
The fourth-round defeat ended her title defense before the quarterfinals. Pegula, a close friend and fellow American, advanced after controlling both sets. The other choices are notable players but were not the defending champion: Naomi Osaka and Aryna Sabalenka had different Australian Open histories, while Elena Rybakina was not the reigning women’s singles winner.