| 2021 season | |||
|---|---|---|---|
 | |||
| General manager | Dave Kasper (until April 14) Lucy Rushton (from April 14) | ||
| Head coach | Hernán Losada | ||
| Stadium | Audi Field | ||
| MLS | Conference: 8th Overall: 16th | ||
| MLS Cup Playoffs | Did not qualify | ||
| U.S. Open Cup | Canceled | ||
| Atlantic Cup | Winners | ||
| Capital Cup | Winners | ||
| Top goalscorer | League: Ola Kamara (19) All: Ola Kamara (19) | ||
| Highest home attendance | 18,034 (10/16 v. NSH) | ||
| Lowest home attendance | 3,935 (5/13 v. CHI) | ||
| Average home league attendance | 12,791 | ||
| Biggest win | DC 7–1 TOR (7/3) | ||
| Biggest defeat | NYCFC 6–0 DC (10/23) | ||
|
| |||
The 2021 D.C. United season was the club's 26th season of existence, and their 26th consecutive season playing in Major League Soccer, the top flight of American soccer. Due to the COVID-19 pandemic and its ongoing vaccination efforts, the season began on April 17, 2021 (about six weeks later than normal) and ended on November 7, 2021. Despite winning against Toronto FC on the last match of the regular season, the team did not qualify playoffs, making it their second consecutive season in which D.C. United did not qualify for the playoffs. It was the first time since 2011, that United did not qualify for the playoffs in consecutive seasons.
Beyond MLS play, D.C. United would have participated in the 2021 U.S. Open Cup, which was initially to begin on May 4, before again being delayed by about six weeks and then ultimately being canceled in July due to the COVID-19 pandemic.