Seiji Miyaguchi (宮口 精二, Miyaguchi Seiji, November 15, 1913 – April 12, 1985) was a Japanese actor who appeared in films of Akira Kurosawa, Yasujirō Ozu, Mikio Naruse, Tadashi Imai and many others. He succumbed to lung cancer at the age of 71.

Distinctions
One of Kurosawa's iconic Seven Samurai, Miyaguchi won the 1955 Mainichi Film Concours Best Supporting Actor award for his role.

In 1983 he was awarded Japan's Medal with Purple Ribbon.

A character designed as a caricature of Miyaguchi is regularly featured in the cat-oriented manga Mon-chan and Me, published in Fusosha's popular webzine Joshi Spa! (Women's Spa!).