Emperor Nintoku (仁徳天皇) was the 16th imperial ruler of Japan. No firm dates can be assigned to this emperor or to his reign, but he is considered to have ruled the country during the early 5th century CE.

According to Nihonshoki, he was the fourth son of Emperor Ojin and the father of Emperors Richu, Hanzei, and Ingyo. The book also states that Nintoku ruled from 313 till 399 but modern research suggests those dates are likely inaccurate.

Scholars identify him with King San of Japan or King Chin in the Chinese history book, Book of Song . According to the Book of Song, San sent messengers to Song Dynasty China at least twice in 421 and 425, and died before 438. Chin was the younger brother of San and sent messengers in 438 to have the Song dynasty assure that his position as the King of Japan was accepted.

Oyama-Kofun (the biggest tomb of the world) in Sakai, Osaka is considered his tomb by most scholars.