Ryū Yamaguchi is a Japanese voice actor affiliated with the talent agency Production Baobab. He was born in Yamaguchi Prefecture on November 2, 1973.

Yamaguchi has built a career as a supporting voice actor, contributing to a wide range of anime series and films across multiple decades. One of his notable and recurring roles is Kyūju Amagiri, a demon working under Kazama Chikage, in the long-running Hakuoki franchise. He has voiced this character in several adaptations, including the original Hakuoki: Demon of the Fleeting Blossom television series, its sequel Record of the Jade Blood, the OVA series A Memory of Snow Flowers, the television short Hakuoki: Otogisōshi, and the film Warrior Spirit of the Blue Sky.

His filmography includes roles in several major anime productions. He is credited with various roles in the long-running series Gintama, including characters named Chaahan, Souan, and Kanekashi. In the Bleach series, he has voiced multiple characters, including a Shinigami and Staff B in the original run, and later took on the role of PePe Waccabrada in the Bleach: Thousand Year Blood War arc. Other credits include Tezcatlipoca in Shakugan no Shana Final, Fernando in the film The Princess and the Pilot, and Tristan Baret in Shoukoku no Altair. His more recent work includes the role of Moroyasu Kono in The Elusive Samurai in 2024.

Throughout his career, Yamaguchi has demonstrated a pattern of appearing in long-running and multi-season franchises, contributing voices to various characters within those worlds, as seen in his work for Bleach, Gintama, and Hakuoki.