2021 League of Ireland First Division

The 2021 League of Ireland First Division season was the 37th season of the League of Ireland First Division, the second tier of Ireland's association football league. The fixture list was released on 8 February 2021 and the competition commenced on 26 March 2021. Shelbourne were confirmed Champions and promoted to the League of Ireland Premier Division on 1 October 2021.

Overview
The First Division has 10 teams. Each team plays each other three times for a total of 27 matches in the season.

Team changes
Shelbourne and Cork City joined following their relegation from the Premier League at the end of the 2020 season. Drogheda United and Longford Town departed following their promotion from the 2020 First Division.

Additional teams
On 10 November 2020 a newly formed Limerick based club Treaty United announced that they would apply for a 2021 League of Ireland licence. Former Dublin based League of Ireland club St Francis FC and Wexford based Yola FC also both expressed interest in joining for 2021 by the deadline for expressions of interest which was 10 November 2020. An application was made by a brand new entity under the name Dublin County F.C. but did not ultimately materialise. Bray Wanderers and Cabinteely F.C. merged at the end of the season, keeping the name Bray Wanderers.

Personnel and kits
Note: Flags indicate national team as has been defined under FIFA eligibility rules. Players may hold more than one non-FIFA nationality.

Matches 1–18
Teams play each other twice (once at home, once away).

*Note Cabinteely v Galway Utd postponed on 9 April 2021 (Galway awarded a 3-0 victory by FAI ).

Top scorers

 * As of matches played 29 October 2021.