Isaac Gerald Mattson (born July 14, 1995) is an American professional baseball pitcher in the Pittsburgh Pirates organization.

Mattson attended Harbor Creek High School in Harborcreek, Pennsylvania, where he played both baseball and basketball.

After his sophomore year, he played for the Chatham Anglers of the Cape Cod Baseball League and was named an all-star.

[5] After signing, Mattson made his professional debut with the Arizona League Angels before being promoted to the Orem Owlz, where he was named an All-Star.

[7] In 2018, he played for the Burlington Bees and the Inland Empire 66ers, going 7–4 with a 3.82 ERA in 25 games (11 starts),[8] and in 2019, he began the year with the 66ers before being promoted to the Mobile BayBears in May.

[14] Mattson made his major league debut on May 7, pitching 2/3 of an inning and allowing one run on a Marwin González RBI double.

[20] On March 31, 2023, Mattson signed with the Southern Maryland Blue Crabs of the Atlantic League of Professional Baseball.

[24] He began 2024 with the Double–A Altoona Curve, and was later promoted to the Triple–A Indianapolis Indians, compiling a 7–2 record and 3.17 ERA with 89 strikeouts over 37 total games.