Yūji Koseki (古関 裕而, Koseki Yūji, August 11, 1909 – August 18, 1989) was a Japanese ryūkōka, gunka, march, fight song and film score composer.

His real name was also Yūji Koseki, but its kanji was 古關 勇治.

He composed Hanshin Tigers' song "Rokko Oroshi" in 1936.

His famous military song titled "Roei no Uta" (露営の歌, lit.

Music for films: This article about a Japanese musician is a stub.