Matthias Tass (born 23 March 1999) is an Estonian basketball player for Legia Warsaw of the Polish Basketball League (PLK). Standing at 2.08 m (6 ft 10 in), he plays at the power forward and center positions. He played college basketball for the Saint Mary's Gaels.

His second season in college was cut short as a result of a torn ACL in right knee in December 2019. Coming into his junior season, Tass was named to the Preseason All-West Coast Conference team. He averaged 10.9 points and 5.3 rebounds per game as a junior. As a senior, Tass was named first-team All-West Coast Conference.

He has played for TTÜ of the Korvpalli Meistriliiga (KML) and the Baltic Basketball League (BBL). Before joining TTÜ in December 2017 he played for Estonian champions Kalev/Cramo.

On August 14, 2022, he has signed with Aquila Basket Trento of the LBA. On August 20, 2022, Tass joined MKS Dąbrowa Górnicza of the Polish Basketball League on loan.

On November 13, 2022, he signed with Baxi Manresa of the Liga ACB.

On July 10, 2025, he signed with Legia Warsaw of the Polish Basketball League (PLK).