Stephanie Louise Gilmore (born 29 January 1988) is an Australian professional surfer and eight-time world champion on the women's World Surf League (WSL) professional tour. She is considered to be one of the greatest surfers of all time, with the most world titles and event victories in the history of the women's WSL and its predecessor, the Association of Surfing Professionals (ASP). She also remains the only surfer in history of the professional tour to win a world title in their debut season of the tour, going on to win four world titles in a row from 2007 to 2010.

Gilmore began her professional career as a 17-year-old, winning her first event as a wildcard in 2005, qualifying for the professional tour two years later. After her run of four consecutive world titles, she won her fifth world title in 2012, after being injured throughout 2011. Her sixth world title in 2014 is considered to be one of the most exciting seasons in women's surfing, with the race coming down to the final heat of the season. After three seasons of inconsistent form, Gilmore won her seventh world title in 2018. Her eighth world title in 2022 came under unique circumstances. Ranked as the fifth seed in the WSL final, she won every heat throughout the day to beat rival Carissa Moore and emerge as champion. She took a competitive hiatus in 2024 and 2025.

Gilmore is credited with pushing women's surfing to equal standing with the men's event, both as a competitor and as an advocate. She was a driving force behind the women's tour receiving equal prize money to the men and equal priority in competitive wave selection. She is also one of Australia's most endorsed athletes, named the highest-earning Australian female athlete in 2015, with her contracts with Rip Curl and Quiksilver's female-focused brand Roxy among the most lucrative in Australian surfing.

Gilmore was born in Murwillumbah, New South Wales. Her father was a surfer, who Gilmore described as "a bit of a hippy", while her mother worked as a primary school teacher. She has two older sisters, Bonnie and Whitney.

She began to surf when her father would pick her up after school, and go to their local beach in Kingscliff, with Gilmore asked to decide to wait on the beach or come surfing, choosing the latter. Her first experience in the surf was riding a boogie board in the waves while being "towed" by her father at the age of nine. She would surf regularly with him, calling her love for the sport "a healthy addiction" and was "not something to take too seriously." Her family would drive to Byron Bay during school holidays to surf and "pull up at the caravan park and pitch the tent, and mum and dad would just hang out while we'd all go surfing at the Pass."

She attended Kingscliff High School, sitting her Higher School Certificate days after winning her second junior world-title and graduated from Year 12 in 2005.

While completing her final year of school, Gilmore began competing in world tour events as a wild card competitor, which included a victory at the 2005 Roxy Pro Gold Coast.

In her next season, Gilmore won another event as a wild card, the 2006 Beachley Classic, defeating the event's namesake, Layne Beachley in the final, a moment considered to be a 'changing of the guard'. In addition to wild card appearances, Gilmore joined the ASP Qualifying Series, finishing second overall and qualifying for the 2007 ASP World Tour.