Somdet Phra Borommaracha Thirat IV (Thai: สมเด็จพระบรมราชาธิราชที่ 4) or Somdet Phra Borommarachathirat No Phutthangkun (Thai: สมเด็จพระบรมราชาหน่อพุทธางกูร), formerly Prince Athittayawong, was the short-reigning king of Ayutthaya from 1529 to 1533. Prince Athittayawong was the son of Ramathibodi II and became the Uparaja in 1515. Following his father's death, Athittayawong succeeded the Ayutthayan throne as Borommaracha IV. He appointed his brother, Prince Chairachathirat, as the Uparaja at Phitsanulok. Borommaracha IV died abruptly in 1533 due to a smallpox epidemic, leaving the throne to his five-year-old son, Prince Ratsadathirat.