Rienk Johannes Mast (born 19 July 2001) is a Dutch college basketball player for the Nebraska Cornhuskers.

After a couple of years, he changed teams to RTC Noord where he was coached by Marco van den Berg.

[4] On 1 February 2018, Mast scored 24 points in a NBB Cup game against Racing Beverwijk, which made him the youngest top scorer for Donar in history.

[5] In the 2017–18 season, Mast started in 3 of the 29 games he played for Donar and averaged 3.6 points and 2.0 rebounds in the Dutch Basketball League.

[13] He explained his move by stating that "Bradley is a great basketball spot, [...] but you get to play against high majors 4-5 times a season.

On November 16, 2018, Mast was selected by head coach Toon van Helfteren to be a part of the Netherlands senior team for the first time.