Rafael Nadal and Iga Swiatek were Thursday named world champions by the International Tennis Federation (ITF) after a season in which they claimed two Grand Slam titles apiece.
Nadal swept to the Australian Open and then backed it up with a 14th French Open, taking his majors total to a men's record of 22.
Swiatek, who inherited the world number one spot in March following the shock retirement of Ashleigh Barty, claimed a second French Open and then captured the US Open.
"I'm very happy to be named ITF World Champion for the fifth time," said 36-year-old Nadal.
"When I first won the award in 2008, I would not have expected to still be playing at such a high level 14 years later."
Nadal also made the semi-finals at Wimbledon but was forced to quit before facing Nick Kyrgios due to an abdominal strain.
Rajeev Ram of the United States and Great Britain's Joe Salisbury are first-time winners of the men's doubles world champion award after claiming their third Grand Slam title together at the US Open and then taking the ATP Finals title for the first time in November.
Barbora Krejcikova and Katerina Siniakova won the women's doubles prize for the third time. The Czech pair won three Grand Slam titles, triumphing at the Australian Open, Wimbledon and US Open.
