Ryoichi Adachi (安達 了一, Adachi Ryōichi, born January 7, 1988) is a Japanese former professional baseball infielder.

He played in Nippon Professional Baseball (NPB) from 2012 to 2024 for the Orix Buffaloes.

Adachi was selected to play in the 2018 NPB All-Star game [jp].

[1] On September 13, 2024, Adachi announced that he would be retiring following the conclusion of the season.

[2] This biographical article relating to a Japanese baseball infielder is a stub.