Caroline Wozniacki was born in Odense, Denmark, on 11 July 1990 into a sporting family of Polish descent. Her father Piotr, a former professional footballer, became her coach in 2004 and stayed in that role for almost all of her career; her mother Anna played for the Polish national volleyball team. As a junior she won the Orange Bowl in 2005 and the Wimbledon girls' title in 2006.
Wozniacki was famous for her footwork, fitness and defence, backed by a reliable two-handed backhand, and she rose fast. At 19 she reached the 2009 US Open final, losing to Kim Clijsters. On 11 October 2010 she became world No. 1, and she finished both 2010 and 2011 at the top, 71 weeks in all, although the major title still eluded her. Injuries to her ankle and knee troubled her between 2013 and 2016, and in 2014 she lost a second US Open final, to Serena Williams.
Her late peak came in 2017 and 2018. She won the WTA Finals at the end of 2017, and in January 2018 she finally won a major at the Australian Open, beating Simona Halep in the final. In all she won 30 singles titles and two doubles titles.
Wozniacki retired after the 2020 Australian Open and from 2022 worked as a commentator for Tennis Channel and ESPN. In 2023, after three years away, she came back at the Canadian Open and the US Open, with her father again as coach, and she played several events in 2024. Late that year she stepped away again while expecting her third child. In November 2025 she said, "I think it's over", though without fully ruling out a return.