| Year: | 2021 |
| Conference: | Horizon League |
| Division: | I |
| Gender: | Men's |
| Teams: | 12 |
| Arena: | Campus sites (First Round and Quarterfinals) Indiana Farmers Coliseum |
| City: | Indianapolis, Indiana (Semifinals and Finals) |
| Champions: | Cleveland State |
| Titlecount: | 2nd |
| Coach: | Dennis Gates |
| Coachcount: | 1st |
| Mvp: | Torrey Patton |
| Mvpteam: | Cleveland State |
| Television: | ESPN+, ESPNU, ESPN2, ESPN |
The 2021 Horizon League men's basketball tournament was the final event of the 2020–21 men's basketball season for the Horizon League. It began on February 25, 2021, and ended on March 9; first-round and quarterfinal games were played at the home courts of the higher seed, with all remaining games at Indiana Farmers Coliseum in Indianapolis. The winner received the conference's automatic berth into the NCAA Tournament.
All of the teams participated in the tournament with the top-four teams receiving byes to the quarterfinals. Due to the unbalanced nature of the conference schedule because of COVID-19, teams were seeded by an unpublished formula generated by the league that took into account the following:[1]
| Seed | School | Winning pct | Strength of schedule | Road Wins / Home Wins | League games played | |
|---|---|---|---|---|---|---|
| 1 | Cleveland State | .800 | 8 / 8 | 20 | ||
| 2 | Wright State | .800 | 8 / 8 | 20 | ||
| 3 | Oakland | .500 | 6 / 4 | 20 | ||
| 4 | Northern Kentucky | .611 | 5 / 6 | 18 | ||
| 5 | Detroit | .625 | 4 / 6 | 16 | ||
| 6 | Youngstown State | .450 | 4 / 5 | 20 | ||
| 7 | Green Bay | .400 | 2 / 6 | 20 | ||
| 8 | Milwaukee | .412 | 4 / 3 | 17 | ||
| 9 | IUPUI | .438 | 4 / 3 | 16 | ||
| 10 | Purdue Fort Wayne | .300 | 2 / 4 | 20 | ||
| 11 | UIC | .375 | 1 / 5 | 16 | ||
| 12 | Robert Morris | .200 | 1 / 2 | 15 |
| Game | Time[2] | Matchup | Score | Television | |||
|---|---|---|---|---|---|---|---|
| First Round – Thursday, February 25 | |||||||
| align=center | 1 | 7:00 pm | align=center | No. 12 Robert Morris at No. 5 Detroit Mercy | align=center | 73–83 | ESPN+ |
| align=center | 2 | 8:00 pm | align=center | No. 11 UIC at No. 6 Youngstown State | 58–74 | ||
| align=center | 3 | 8:00 pm | align=center | No. 10 Purdue Fort Wayne at No. 7 Green Bay | align=center | 89–84 | |
| align=center | 4 | 8:00 pm | align=center | No. 9 IUPUI at No. 8 Milwaukee | align=center | 72–84 | |
| Quarterfinals – Tuesday, March 2 | |||||||
| align=center | 5 | 7:00 pm | align=center | No. 10 Purdue Fort Wayne at No. 1 Cleveland State | align=center | 104–108 | ESPN+ |
| align=center | 6 | 7:00 pm | align=center | No. 5 Detroit Mercy at No. 4 Northern Kentucky | align=center | 69–70 | |
| align=center | 7 | 7:00 pm | align=center | No. 8 Milwaukee at No. 2 Wright State | align=center | 94–92 | |
| align=center | 8 | 7:30 pm | align=center | No. 6 Youngstown State at No. 3 Oakland | align=center | 83–87 | |
| Semifinals – Monday, March 8 at Indiana Farmers Coliseum, Indianapolis, IN | |||||||
| align=center | 9 | 6:30 pm | align=center | No. 8 Milwaukee vs. No. 1 Cleveland State | align=center | 65–71 | ESPNU |
| align=center | 10 | 9:30 pm | align=center | No. 4 Northern Kentucky vs. No. 3 Oakland | align=center | 58–69 | ESPN2 |
| Championship – Tuesday, March 9 at Indiana Farmers Coliseum, Indianapolis, IN | |||||||
| 11 | 7:00 pm | No. 1 Cleveland State vs. No. 3 Oakland | 80–69 | ESPN | |||
| All game times Eastern. Rankings denote tournament seed | |||||||
* denotes overtime period