Toshiaki Sakai (born 9 April 1974) is a Japanese former professional tennis player.

A left-handed player from Tokyo, Sakai made his only ATP Tour main draw appearances at the 1995 Japan Open, but didn't begin competing professionally until 2002.

[1] Sakai, who is the son of Universiade champion Toshiro Sakai, was a student at Keio University and represented Japan at the 1995 Summer Universiade.

He won the All Japan Student Tennis Championships singles title in 1996.

[2] On the professional tour, Sakai reached a best singles ranking of 468 in the world and featured in the qualifying draw for the 2003 Australian Open.