Kidinnu (also Kidunnu) (fl. 4th century BC? possibly died 14 August 330 BC) was a Chaldean astronomer and mathematician. Strabo of Amaseia called him Kidenas, Pliny the Elder Cidenas, and Vettius Valens Kidynas.

Kidinnu is an impact crater on the Moon's far side. It lies to the south of the H. G. Wells crater and to the southeast of Cantor crater.