Gustavo Kuerten (Portuguese pronunciation: [ɡusˈtavu ˈkiɾtẽ]; born September 10, 1976) is a retired former World No. 1 tennis player from Brazil. He won the French Open three times between 1997 and 2001, and was the Tennis Masters Cup champion in 2000. After 12 years on the international tour, he retired from top-level tennis in May 2008.

Kuerten is also known as "Guga" (pronounced: [ˈɡuɡɐ]), an affectionate nickname which is a common abbreviation of the name "Gustavo" in Portuguese-speaking countries. He is a polyglot who speaks fluent Portuguese, Spanish, English and French.^{[citation needed]}

Kuerten was born in Florianópolis in southern Brazil. He comes from an ethnically German family. He began playing tennis when he was six, an early start to a life and career marked by family tragedy. His father, a former amateur tennis player, died of a heart attack in 1985 while umpiring a junior tennis match in Curitiba, when Kuerten was only eight years old. His older brother, Raphael, is currently his business manager. His youngest brother suffered prolonged oxygen deprivation and consequently irreparable brain damage during birth, and as a result suffered from mental retardation and severe physical disability until his death in 2007. Kuerten was deeply affected by his brother's daily struggles, later donating the entire prize money from one tournament he has won every year of his professional career so far to a hometown NGO that provides assistance for people suffering from similar disabilities. He gave every trophy he won to his younger brother as a souvenir, including the three miniature replicas of the French Open men's singles trophy.