Tsuyoshi Yamaguchi

is a Japanese curler from Karuizawa, Nagano.

Career Yamaguchi has competed at the World Men's Curling Championships six times in his career. At the 2009 Worlds in Moncton, New Brunswick, Canada, he played third for the Japanese team, which placed tenth in the tournament; At the 2013 Worlds in Victoria, British Columbia, Canada, he played third for the Japanese team, which placed 11th in the tournament; At the 2014 Worlds in Beijing, China, he played third for the Japanese team, which placed fifth in the tournament; At the 2015 Worlds in Halifax, Nova Scotia, Canada, he played as third for the Japanese team, which placed sixth in the tournament; At the 2016 Worlds in Basel, Switzerland, he played second for the Japanese team, which placed fourth in the tournament; and at the 2017 Worlds in Edmonton, Alberta, Canada, he played second for the Japanese team, which placed seventh in the tournament. He played second for Yusuke Morozumi rink and represented Japan at the 2018 Winter Olympics, finishing in 8th place.

Mixed doubles Yamaguchi represented Japan with Satsuki Fujisawa at the 2018 World Mixed Doubles Curling Championship, finishing in 5th place. The pair again represented Japan at the 2019 World Mixed Doubles Curling Championship, finishing in 5th once again. In 2024, Yamaguchi partnered with Miyu Ueno, and in their first year together, won the Japan Mixed Doubles Curling Championship. The pair represented Japan at the 2024 World Mixed Doubles Curling Championship, finishing the round robin at 6–3 and in 9th place. Due to their win at the 2024 national championships, the pair also qualified for the 2025 Japanese Olympic mixed doubles curling trials. At the national Olympic trials, the team finished a disappointing 0–4.

Personal life Yamaguchi is employed as a curling club manager and commentator. He is married.