The 1981 Lamar Cardinals football team represented Lamar University in the 1981 NCAA Division I-A football season as a member of the Southland Conference. The Cardinals played their home games at Cardinal Stadium now named Provost Umphrey Stadium in Beaumont, Texas. Lamar finished the 1981 season with a 4–6–1 overall record and a 1–3–1 conference record. A highlight for the season was a last second victory over the defending Southwest Conference champion Baylor Bears at the Bears' home field, Floyd Casey Stadium in Waco, Texas.