Kasat Suek (Thai: กษัตริย์ศึก, pronounced [kā.sàt sɯ̀k]) refers to an intersection and its corresponding bridge on the periphery of Pom Prap Sattru Phai and Pathum Wan Districts, Bangkok.

[1][2][3] "Kasat Suek" translates as 'king of war' and comes from the title Somdet Chaophraya Maha Kasatsuek (สมเด็จเจ้าพระยามหากษัตริย์ศึก), which belonged to King Phutthayotfa Chulalok (Rama I), founder of the Chakri dynasty and namesake of the road the bridge is on, before he became king.

In the past, the intersection was known as the site of a movie theater named "Chaloem Khet" (เฉลิมเขตร์) after Princess Chalermkhetramongmol, Prince Bhanurangsi Savangwongse's youngest daughter.

The theater was later demolished, though the name still exists with the alleys in this area being called Soi Chaloem Khet.

[4] In 1907, Kasat Suek saw the first bus route in Bangkok (and all of Thailand), developed by Phraya Bhakdi Noraset (Nai Lert), which ran from the bridge along Rama I Road and led up to Pratunam in Pathum Wan District, a distance of about 2.9 kilometres (1.8 mi).