1965–66 Washington State Cougars men's basketball team

The 1965–66 Washington State Cougars men's basketball team represented Washington State University for the 1965–66 NCAA college basketball season. Led by eighth-year head coach Marv Harshman, the Cougars were members of the Athletic Association of Western Universities (AAWU, Pac-8) and played their home games on campus at Bohler Gymnasium in Pullman, Washington.

The Cougars were 15–11 overall in the regular season and 6–8 in conference play, tied for fourth in the standings.

The fifteen wins were the most for Washington State in fourteen years.