Nanda Bayin (; d. November 1600), was the king of the Taungoo Dynasty of Myanmar from 1581 to 1599. Nanda Bayin was the first son of King Bayinnaung. He was made the crown prince upon the ascension of his father in 1551. As the crown prince, he led subjugation of Lanna and the sack of Vientiene in 1565. He also waged wars alongside his father against Ayutthaya that eventually led to the fall of the city in 1564 and 1569.

Bayinnaung died in 1581. Crown Prince Nanda succeeded his father as the king of Pegu and appointed his first son Minchit Sra as the Crown Prince. Thatominthaw the King of Ava (Nanda Bayin’s brother-in-law), however, didn’t attend the coronation audience due to the crown prince’s treatment to the crown princess who was Thatominthaw’s daughter. Nanda Bayin was enraged at the inobedience of his brother-in-law, ordered the massacre of people supporting the King of Ava, and prepared a full-scale war against Ava.

Nanda Bayin also requested auxiliary troops from Prome, Toungoo, and Ayutthaya. The king was also to take Ava with the help of Prome and Toungoo and installed his son Minyekyawswa. The Siamese armies led by crown prince Naresuan, however, marched towards Pegu. Nanda Bayin hurried down south to stop the Siamese from reaching the capital, only to find out that the Siamese prince had returned and sacked Mon cities on the way.

In 1583, Nanda Bayin sent his Burmese armies into Siam led by the crown prince to subjugate the country. The campaign, however, failed. Nanda Bayin decided to lead the armies himself into Siam in 1586 and reached Ayutthaya but laid siege on the city for five months without success. Then Nanda Bayin decided to retreat but was followed and harassed by Siamese armies. In 1590, the king marched into Siam again with Minchit Sra in the vanguard, but the crown prince was again defeated by the Siamese led by Naresuan.

Nanda Bayin then mustered all available forces at his disposal aganist the Siamese. In 1592, a very large campaign was organized and the Burmese armies amassed towards Ayutthaya led by the crown prince. The Burmese and Siamese battled near Ayutthaya (see Battle of Nong Sarai and Yuttahadhi) and the crown prince and King Naresuan of Ayutthaya engaged a personal elephant battle, which resulted in Minchit Sra’s death.

With the death of Minchit Sra, Nanda Bayin appointed Minyi Kyawshwa the King of Ava as the crown prince. Nanda Bayin suffered several Mon rebellions around the city of Martaban and Moulmein that led to the expansion of Siamese influence into the Mon state. In 1594, Naresuan, with the supports from the Mon rebels, marched towards Pegu and laid siege on the city but then retreated due to an aggressive defence by the Kingdoms of Prome and Toungoo.

In 1595, however, the King of Prome who was Nanda Bayin’s son led a huge rebellion taking Toungoo and a large northern portion of the kingdom, proclaiming himself as an independent king. Nanda Bayin then lost trust in those close to him and requested the sons of tributary kings to be held hostage in Pegu. The King of Toungoo then requested the King of Rakhine to invade Pegu and made Toungoo king. The Arakan invasion was countered by the crown prince but the crown prince then gave himself up to Toungoo – where he was killed by Natshinnaung. Shocked by the death of his son and his own defeat, Nanda Bayin gave up the throne to the King of Toungoo in 1599 and was captured to Toungoo – therefore his epithet Toungooyawk Min (the king who was captured to Toungoo).

The abdicated king had survived for an another year before being assassinated by Natshinnaung in 1600.