Borommarachathirat IV (Thai: บรมราชาธิราชที่ ๔; also spelt Borom Rachathirat IV), also known as Borommaracha No Phutthangkun (Thai: บรมราชาหน่อพุทธางกูร; also spelt Borom Racha No Buddhakura), born Athittayawong (Thai: อาทิตยวงศ์), was the short-reigning king of Ayutthaya from 1529 to 1533.

Borommarachathirat was born Prince Athittayawong to Ramathibodi II in 1488. He was named uparaja (heir presumptive and viceroy) at Phitsanulok in 1515.

Following his father's death, Athittayawong succeeded the throne as Borommarachathirat IV. He appointed his brother, Prince Chairachathirat, as uparaja. Borommarachathirat died abruptly in 1533 due to a smallpox epidemic; however, counter to the tradition established by the Front Palace system, the throne passed not to the uparaja but to Borommarachathirat's five-year-old son, who would rule as Ratsadathirat.^{[2]: 72 [3]: 37}