Maharana Udai Singh (1522–1572) was king of Mewar and founder of the city of Udaipur in Rajasthan.

He was the 53rd ruler of the Mewar dynasty. He was the son of Maharana Sangram Singh and Rani Karmavati. Panna Dhai saved him from his uncle Banbir. He lived in Kumbhalgarh for two years. He was crowned king in 1540. He was father of Maharana Pratap. He died in 1572 at Gogunda.

During his childhood Udai Singh was twice saved in extraordinary circumstances. First he was smuggled out of Chittor before the sack by the Sultan of Gujarat. Then, to save him from his uncle Banbir who was regent and wished to usurp the throne, his faithful nurse Panna Dai substituted her own baby in the royal cradle. Her child was slain, but Panna escaping with the baby prince made her way to Kumbalgarh fort, where Udai was brought up. Banbir was killed by palace intrigue and Udai Singh was restored to the throne.

It was during Udai's reign that the Moghul Emperor Akbar besieged Chittor (1568). The Rana left the fort to be defended by his brave vassal chiefs, Jaimal and Patta, fifteen year old lads. Akbar was victorious. The Rajputs having seen their women and children immolated, died fighting. Chittor never recovered from this third attack and Udai Singh built his new capital at Udaipur.