Thomas Costigan (born August 26, 1997) is a professional gridiron football defensive lineman who is a free agent.

[1][2] Costigan signed with the Los Angeles Chargers as an undrafted free agent on August 12, 2019.

[6] He played in 11 regular season games that year where he recorded 24 defensive tackles and lead the team with six sacks.

[2] On August 31, 2022, Costigan was traded to the Montreal Alouettes along with Nafees Lyon for Avery Ellis and a third-round pick in the 2023 CFL Draft.

[8] On the first day of free agency, on February 14, 2023, it was announced that Costigan had signed with the Toronto Argonauts.