Triam Udom Suksa School (Thai: โรงเรียนเตรียมอุดมศึกษา, pronounced  [trīːam ùdōm sɯ̀k.sǎː], lit. "university-preparatory school") is a state school located in downtown Bangkok, Thailand. It admits upper-secondary students (mathayom 4–6, equivalent to grades 10–12) and has the largest yearly enrolment in the country. Founded in 1938 as a preparatory school for Chulalongkorn University, the school has long been regarded as one of the best secondary schools in Thailand, and attracts students from all over the country in its highly competitive entrance examinations.