The 1983–84 Lamar Cardinals basketball team represented Lamar University during the 1983–84 NCAA Division I men's basketball season.

The Cardinals were led by fourth-year head coach Pat Foster and played their home games at the Beaumont Civic Center in Beaumont, Texas as members of the Southland Conference.

The Cardinals won the regular season conference championship.

They received an invitation to the 1984 National Invitation Tournament where they defeated New Mexico in the first round and lost to Santa Clara in the second round.

Lamar finished the season with a record of 26–5 (11–1 Southland).