Kotaro Miyachi (Japanese: 宮地 弘太郎, born 18 February 1974) is a Japanese former professional tennis player. Born in Fukuyama, Miyachi was a World Youth Cup (Junior Davis Cup) representative for Japan in 1990, securing a win over future world number one Marcelo Ríos. Miyachi was a singles bronze medalist at the 1995 Summer Universiade.