Empress Kojun (????, Kojun-kogo), born Princess Nagako (????, Nagako Joo, 6 March 1903 – 16 June 2000), was the wife of Emperor Showa (Hirohito) of Japan.
She was the mother of the emperor emeritus, Akihito.
Her posthumous name is Kojun, which means "fragrant purity".
Empress Kojun was empress consort (kogo) from 25 December 1926 to 7 January 1989, making her the longest-serving empress consort in Japanese history.