The 1999–2000 Oklahoma State Cowboys basketball team represented Oklahoma State University as a member of the Big 12 Conference during the 1999–2000 NCAA Division I men's basketball season.
They were led by 10th-year head coach Eddie Sutton and played their home games at Gallagher-Iba Arena in Stillwater, Oklahoma.
The Cowboys lost to Iowa State in the semifinals of the Big 12 tournament.
The team received an at-large bid to the NCAA tournament as the No.
Oklahoma State reached the Elite Eight after wins over Hofstra, Pepperdine, and Seton Hall, but lost in the regional final to Florida.