Eita Nagayama (永山 瑛太, born December 13, 1982), occasionally credited mononymously as Eita, is a Japanese actor from Tokyo. He has appeared in many Japanese television dramas and movies; most notable is the TV series Water Boys. He also appeared in Summer Time Machine Blues and Tokyo Friends: The Movie.

In 2009, Eita was cast in his first theatrical role playing a human in a romantic relationship with a female ghost.^[1] Not long after in August 2009, it was announced that Eita had been cast as the lead in the play Tokyo Gekko Makyoku, playing a mysterious character living in the early Shōwa era. It was his first time playing the lead in a theatrical production.^[2]

Nagayama is to appear with Jun Matsumoto and Masami Nagasawa in Hideki Noda's Sei sankaku kankei (正三角関係, Trilateral connection). Performances are expected at the Tokyo Metropolitan Theatre, in Kitakyushu and Osaka, as well as Sadler's Wells Theatre in London, under the name of "Love in action", running from July 11 until November 2, 2024.^[3]

On June 1, 2010, it was announced that Eita would marry singer Kaela Kimura, who was already five months pregnant, that summer after becoming engaged in late 2009.^[4][5] Eita and Kimura announced that they submitted their marriage registration on September 1, 2010.^[6]