Mahinthrathirat (Thai: มหินทราธิราช) (1539–1569) was king of Ayutthaya 1564 to 1568 and again in 1569. He ruled his first reign as a vassal of Toungoo Burma before restoring his father in 1568 as the sovereign king. He became king again in 1569 after his father's death during the Third Siege of Ayutthaya by Toungoo forces. Mahinthrathirat was the last monarch of the Suphannaphum Dynasty as the kingdom fell to the Burmese in 1569. Mahinthrathirat was known for his efforts to counter Burmese and Phitsanulok power by seeking alliance with Setthathirath of Lan Xang.

Prince Mahinthrathirat was a son of Maha Chakkrapat and Queen Sri Suriyothai. Mahinthrathirat had an elder brother Prince Ramesuan the Uparaja - then heir to the throne. In 1548, Tabinshweti marched the Burmese armies to invade Ayutthaya. Mahinthrathirat joined his family to battle the Burmese. However, his mother Queen Sri Suriyothai was killed in battle.

Bayinnaung, brother-in-law of Tabinshweti, led the Burmese to invade Ayutthaya again in 1563. Bayinnaung laid the siege on Ayutthaya in 1564, and installed Mahin as the vassal king on 18 February 1564.

Maha Thammarachathirat, the King of Phitsanulok and Maha Chakkrapat's handful noble, had allied himself with Bayinnaung since the war of 1563. Maha Chakkrapat sought an alliance with Setthathirat of Lan Xang, through the marriage of his daughter Thepkasattri, but Maha Thammarachathirat informed Bayinnaung about the arranged marriage and alliances. Bayinnaung then kidnapped Thepkasatri on her way to Vientiane. This forced Maha Chakkrapat to abdicate the throne to his son Mahinthrathirat, who planned a joint-attack on Phitsanulok with Setthathirat. Following that failed attack, Mahinthrathirat urged his father to return to regal power in the ensuing crisis.

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