Colin Reed Castleton (born May 25, 2000) is an American professional basketball player for the Osceola Magic of the NBA G League.

As a senior, he averaged 24.5 points, 11.7 rebounds, and 5.6 blocks per game and was named a finalist for Florida's Mr. Basketball Award and the Class 7A Player of the Year.

[2] On November 10, 2017, Castleton tendered his National Letter of Intent as part of a five-man recruiting class that included Ignas Brazdeikis, David DeJulius, Brandon Johns, and Adrien Nunez.

[6][7] Castleton was granted a waiver to make him eligible to play for the Florida Gators immediately rather than have to sit out one season per NCAA transfer rules.

The effort partly recognizes the rare stat line of 16 points, 13 rebounds, six assists, three steals, and two blocked shots against Missouri on January 14.

[24] On October 27, 2024, Castleton joined the Long Island Nets[25] and three days later, he signed a two-way contract with the Memphis Grizzlies.