Kosai

Kosai can stand for:
 * Hiroki Kosai, 20th-century Japanese astronomer
 * Kosai, Shizuoka, Japan, a city
 * Kōsai, a disciple of Hōnen of the Jōdo Shū Buddhist sect
 * Kosai river, near Kharagpur in the Indian state of West Bengal
 * Count Kosai Uchida (or Uchida Yasuya), 19th-20th-century Japanese statesman and diplomat
 * Wiang Kosai, a national park in the Phrae and Lampang provinces of Thailand
 * Kosai or koose, an African pea fritter