Thomas Clark Welsh (born February 3, 1996) is an American professional basketball player for the Greensboro Swarm of the NBA G League. He played college basketball for the UCLA Bruins. As a senior in 2017–18, Welsh earned second-team all-conference honors in the Pac-12. He was selected by the Denver Nuggets in the second round of the 2018 NBA draft with the 58th overall pick.
Welsh was a McDonald's All-American in high school. After leading UCLA in blocks as a freshman reserve, he was a member of the United States national team that won the gold medal at the FIBA Under-19 World Championship in 2015. He started for the Bruins as a sophomore and junior, leading the team in rebounds while also continuing to be their top shot blocker.