The 2008–09 Oklahoma State Cowboys men's basketball team represented Oklahoma State University in the 2008–09 NCAA Division I men's basketball season.

This was head coach Travis Ford's inaugural season at Oklahoma State.

The Cowboys competed in the Big 12 Conference and played their home games at Gallagher-Iba Arena.

They lost in the semifinals of the 2009 Big 12 men's basketball tournament.

They received an at–large bid to the 2009 NCAA Division I men's basketball tournament, earning an 8 seed in the East Region, where they advanced to the Second Round by defeating 9 seed Tennessee 77–75.