The Burmese-Siamese War of 1563–1564, also known as the War over the White Elephants, was a conflict between the Toungoo Dynasty of Burma and the Ayutthaya Kingdom of Siam. King Bayinnaung of the Toungoo Dynasty sought to bring the Ayutthaya Kingdom under his rule, part of a broader ambition to build a large Southeast Asian empire. After initially demanding two white elephants from Ayutthaya King Maha Chakkraphat as tribute and being refused, Bayinnaung invaded Siam with an extensive force, capturing several cities like Phitsanulok and Sukhothai along the way. The Burmese army reached Ayutthaya and initiated a weeks-long siege, which was aided by the capture of three Portuguese warships.

The siege did not lead to the capture of Ayutthaya, but resulted in a negotiated peace at a high cost for Siam. Chakkraphat agreed to make the Ayutthaya Kingdom a vassal state of the Toungoo Dynasty. In exchange for the withdrawal of the Burmese army, Bayinnaung took hostages, including Prince Ramesuan, as well as four Siamese white elephants. Siam also had to give annual tributes of elephants and silver to the Burmese, while allowing them tax-collection rights at the port of Mergui.

The treaty led to a short-lived period of peace lasting until a 1568 revolt by Ayutthaya. Burmese sources claim that Maha Chakkraphat was taken back to Burma before being allowed to return to Ayutthaya as a monk, while Thai sources say that he abdicated the throne and his second son, Mahinthrathirat, ascended. The war was a significant event in the series of conflicts between the Burmese and Siamese, and it temporarily extended the influence of the Toungoo Dynasty over the Ayutthaya Kingdom.