Also included in the 2021 calendar were the Davis Cup (organised by the ITF), the Summer Olympics in Tokyo (rescheduled from 2020), Next Gen ATP Finals, Laver Cup (postponed from 2020), none of which distributed ranking points.

[3][4][5] The COVID-19 pandemic affected tournaments on both the ATP and WTA tours.

The following tournaments were cancelled or postponed due to the COVID-19 pandemic.

The players/nations are sorted by: The following players won their first main circuit title in singles, doubles or mixed doubles: The following players defended a main circuit title in singles, doubles, or mixed doubles: The following players achieved their career high ranking in this season inside top 50 (in bold the players who entered the top 10 for the first time): These are the ATP rankings and yearly ATP race rankings of the top 20 singles players, doubles players and doubles teams at the current date of the 2021 season.

Points are awarded as follows:[20] The following is a list of notable players (winners of a main tour title, and/or part of the ATP rankings top 100 in singles, or top 100 in doubles, for at least one week) who announced their retirement from professional tennis, became inactive (after not playing for more than 52 weeks), or were permanently banned from playing, during the 2021 season: The following is a list of notable players (winners of a main tour title, and/or part of the ATP rankings top 100 in singles, or top 100 in doubles, for at least one week) who returned from retirement during the 2021 season: