The 2021 NCAA Division I FCS football season, part of college football in the United States, was organized by the National Collegiate Athletic Association (NCAA) at the Division I Football Championship Subdivision (FCS) level.

After the prior season was impacted by the COVID-19 pandemic in the United States, resulting in some conferences canceling their seasons and significant rescheduling by other conferences, the 2021 season returned to its traditional fall scheduling. The season ended with a single-elimination tournament, with the championship game held on January 8, 2022 at Toyota Stadium in Frisco, Texas. North Dakota State won its ninth championship in eleven seasons, defeating Montana State, 38-10, for the title.

The following rule changes were approved by the NCAA Playing Rules Oversight Panel on April 22:^[1][2]

• In overtime, teams scoring a touchdown will be required to attempt a two-point conversion starting with the second overtime period (previously the third overtime period) and, if still tied, teams will be required to attempt alternating two point conversions starting with the third overtime (previously the fifth overtime period).
• Permanently extending the team area from between the 25-yard lines to between the 20-yard lines. A rule implemented for the 2020 season amid the COVID-19 pandemic had extended the area to between the 15-yard lines, but it had been scheduled to revert to the 25 for 2021.
• Creating a process for a review panel that can be used by teams and/or conferences for instances of teams feigning injuries to slow down teams' momentum or stop the game clock.
• Explicitly prohibiting video board and lighting system operators from creating "any distraction that obstructs play", with violations being deemed unsportsmanlike conduct.
• If replay overturns a call on the field, the game clock will only be adjusted inside of the last 2:00 of the first half and the last 5:00 of the second half.

• September 4 – In Kevin Kelley's debut as head coach of Presbyterian, Ren Hefley threw for 10 touchdowns in the Blue Hose's 84–43 win over NAIA member St. Andrews, breaking the previous FCS record of 9 first set in 1984 by Willie Totten of Mississippi Valley State and equaled in 2007 by Drew Hubel of Portland State. Blue Hose backup quarterback Tyler Huff added 2 TD passes to set a new Division I team record (for both FCS and FBS) of 12, surpassing the previous record of 11 thrown by David Klingler of Houston against Eastern Washington in 1990.^[3]
• November 12 – The Utah Legislature approved changing the name of FCS member Dixie State University to Utah Tech University, effective in the 2022–23 academic year.^[4]

September 2: UC Davis 19, Tulsa 17
September 3: Eastern Washington 35, UNLV 33
September 3: South Dakota State 42, Colorado State 23
September 4: Holy Cross 38, UConn 28
September 4: Montana 13, No. 20 Washington 7
September 4: East Tennessee State 23, Vanderbilt 3
September 11: Duquesne 28, Ohio 26
September 11: Jacksonville State 20, Florida State 17
September 18: Incarnate Word 42, Texas State 34
September 18: Northern Arizona 21, Arizona 19
November 6: Rhode Island 35, UMass 22
November 13: Maine 35, UMass 10

• The Western Athletic Conference (WAC), which had last played football in the 2012 season as an FBS league, reinstated football for the 2021 season at the FCS level.^[5][6] The ASUN Conference also announced in 2021 that it would sponsor FCS football in the future.
• Because WAC and ASUN programs reclassifying from Division II could not be counted toward the minimum of six members required for a conference champion to be an automatic qualifier (AQ) for the FCS postseason, the two conferences pooled their seven members with active FCS programs in 2021 (four WAC, three ASUN) to form the WAC–ASUN Challenge, a temporary league also referred to as the AQ7.^[7][8][9]

After the prior season's playoffs were reduced to a 16-team bracket, FCS returned to a 24-team bracket for this season: 11 of the teams were decided via automatic bids issued to conference champions (listed above) and 13 teams were determined via at-large bids; the top eight teams were seeded.^[10]

The top 25 from the Stats Perform and USA Today Coaches Polls.

The regular season began with three games on Saturday, August 28:

• Indiana State 26, Eastern Illinois 21
• MEAC/SWAC Challenge at Center Parc Stadium in Atlanta: North Carolina Central 23, Alcorn State 14
• San Jose State (FBS) 45, Southern Utah 14

Rankings reflect the Stats Perform Poll.

• Week 3
  • No. 3 James Madison defeated No. 9 Weber State, 37–24 (Stewart Stadium, Ogden, Utah)
• Week 5
  • No. 6 Eastern Washington defeated No. 4 Montana, 30–24 (Roos Field, Cheney, Washington)
  • No. 5 North Dakota State defeated No. 10 North Dakota, 16–10 (Alerus Center, Grand Forks, North Dakota)
• Week 6
  • No. 8 Southern Illinois defeated No. 2 South Dakota State, 42–41 ^OT (Dana J. Dykhouse Stadium, Brookings, South Dakota)
• Week 10
  • No. 4 Montana State defeated No. 5 Eastern Washington, 23–20 (Roos Field, Cheney, Washington)
  • No. 9 South Dakota State defeated No. 2 North Dakota State, 27–19 (Dana J. Dykhouse Stadium, Brookings, South Dakota)
• Week 11
  • No. 7 Eastern Washington defeated No. 6 UC Davis, 38–20 (UC Davis Health Stadium, Davis, California)
• Week 12
  • No. 6 Montana defeated No. 3 Montana State, 29–10 (Washington–Grizzly Stadium, Missoula, Montana)

This section lists instances of unranked teams defeating ranked teams during the season.

• 2021 NCAA Division I FBS football season
• 2021 NCAA Division II football season
• 2021 NCAA Division III football season
• 2021 NAIA football season