Jelena Ostapenko was 20 when she beat Simona Halep to win the French Open in 2017, but she was a teenager until the Roland Garros semi-finals. Christian Hartmann / Reuters
Evonne Goolagong, 19, beat Helen Gourlay to win the French Open in 1971. Allsport
Chris Evert, 19, beat Olga Morozova in the 1974 French Open final. Getty Images
Bjorn Borg, 18, beat Manuel Orantes to win the French Open in 1974. AFP
Tracy Austin, 16, beat Chris Evert to win the US Open in 1979. Fred R Conrad / Getty Images
Hana Mandlikova, 18, beat Wendy Turnbull to win the Australian Open in 1980. Jean-Yves Ruszniewski / Getty Images
Mats Wilander, 17, beat Guillermo Vilas to win the French Open in 1982. Joel Robine / AFP
Boris Becker, 17, beat Kevin Curren to win Wimbledon in 1985. Bob Thomas / Getty Images
Stefan Edberg, 19, beat Mats Wilander to win the Australian Open in 1985. Bob Dear / AP Photo
Steffi Graf, 17, beat Martina Navratilova to win the French Open in 1987. AFP
Arantxa Sanchez Vicario, 17, beat Steffi Graf to win the French Open in 1989. Simon Bruty / Getty Images
Michael Chang, 17, beat Stefan Edberg to win the French Open in 1989. AFP
Monica Seles, 16, beat Steffi Graf to win the French Open in 1990. Jean-loup Gautreau / AFP
Pete Sampras, 19, beat Andre Agassi to win the US Open in 1990. Carol Newsom / AFP
Martina Hingis, 16, beat Mary Pierce to win the Australian Open in 1997. Clive Brunskill /Allsport
Iva Majoli, 19, beat Martina Hingis to win the French Open in 1997. Jean-Yves Ruszniewski / Getty Images
Serena Williams, 17, beat Martina Hingis to win the US Open in 1999. Timothy A Clary / AFP
Maria Sharapova, 17, beat Serena Williams to win Wimbledon in 2004. Jeff Overs / Getty Images
Svetlana Kuznetsova, 19, beat Elena Dementieva to win the US Open in 2004. Don Emmert / AFP
Rafael Nadal, 19, beat Mariano Puerta to win the French Open in 2005. Clive Mason / Getty Images
Jelena Ostapenko was 20 when she beat Simona Halep to win the French Open in 2017, but she was a teenager until the Roland Garros semi-finals. Christian Hartmann / Reuters
Evonne Goolagong, 19, beat Helen Gourlay to win the French Open in 1971. Allsport
Chris Evert, 19, beat Olga Morozova in the 1974 French Open final. Getty Images
Bjorn Borg, 18, beat Manuel Orantes to win the French Open in 1974. AFP
Tracy Austin, 16, beat Chris Evert to win the US Open in 1979. Fred R Conrad / Getty Images
Hana Mandlikova, 18, beat Wendy Turnbull to win the Australian Open in 1980. Jean-Yves Ruszniewski / Getty Images
Mats Wilander, 17, beat Guillermo Vilas to win the French Open in 1982. Joel Robine / AFP
Boris Becker, 17, beat Kevin Curren to win Wimbledon in 1985. Bob Thomas / Getty Images
Stefan Edberg, 19, beat Mats Wilander to win the Australian Open in 1985. Bob Dear / AP Photo
Steffi Graf, 17, beat Martina Navratilova to win the French Open in 1987. AFP
Arantxa Sanchez Vicario, 17, beat Steffi Graf to win the French Open in 1989. Simon Bruty / Getty Images
Michael Chang, 17, beat Stefan Edberg to win the French Open in 1989. AFP
Monica Seles, 16, beat Steffi Graf to win the French Open in 1990. Jean-loup Gautreau / AFP
Pete Sampras, 19, beat Andre Agassi to win the US Open in 1990. Carol Newsom / AFP
Martina Hingis, 16, beat Mary Pierce to win the Australian Open in 1997. Clive Brunskill /Allsport
Iva Majoli, 19, beat Martina Hingis to win the French Open in 1997. Jean-Yves Ruszniewski / Getty Images
Serena Williams, 17, beat Martina Hingis to win the US Open in 1999. Timothy A Clary / AFP
Maria Sharapova, 17, beat Serena Williams to win Wimbledon in 2004. Jeff Overs / Getty Images
Svetlana Kuznetsova, 19, beat Elena Dementieva to win the US Open in 2004. Don Emmert / AFP
Rafael Nadal, 19, beat Mariano Puerta to win the French Open in 2005. Clive Mason / Getty Images
Jelena Ostapenko was 20 when she beat Simona Halep to win the French Open in 2017, but she was a teenager until the Roland Garros semi-finals. Christian Hartmann / Reuters