Shintaro Mochizuki (Japanese: 望月 慎太郎, Mochizuki Shintaro, born 2 June 2003) is a Japanese tennis player. He has an ATP career-high singles ranking of world No. 348 achieved on 18 July 2022. Mochizuki has a career high ITF junior combined ranking of No. 1 achieved on 15 July 2019. Mochizuki won the 2019 Wimbledon Championships – Boys' singles title after becoming the first Japanese male to reach a Grand Slam juniors singles final. In September that year, he led the Japanese team to win the Junior Davis Cup in Orlando, Florida.