Karol Welter is a Polish professional boxer.
Welter made his professional debut on 20 January 2018 where he beat David Schwierz via majority decision (MD).
His first title match came on 3 September 2021 where he fought against Przemysà Âaw Gorgoà  for the Republic of Poland Super Middleweight title. This would be his first career loss after losing via split decision (SD).
His second chance for a title came on 15 April 2023 where he faced off against Stanisà Âaw Gibadlo for the vacant Republic of Poland middleweight title. Welter won the fight via unanimous decision (UD).
He faced Misto Abdulaev on November 29, 2025, for the vacant WBA Baltic and Republic of Poland International middleweight titles. Welter won the fight via a fourth-round TKO.
His first defense of both titles came on March 6, 2026, against Evander Castillo. Welter won the fight via a third-round knockout.