The University of Santo Tomas (UST; Filipino: Unibersidad ng Santo Tomás), officially the Pontifical and Royal University of Santo Tomas, The Catholic University of the Philippines or colloquially as Ustê (pronounced [usˈtɛʔ]), is a private Catholic research university in Manila, Philippines. Founded on April 28, 1611, by Spanish friar Miguel de Benavides, third Archbishop of Manila, it has the oldest extant university charter in Asia and is one of the world's largest Catholic universities in terms of enrollment found on one campus. It is the main campus of the University of Santo Tomas System that is run by the Order of Preachers.

UST was granted the title Royal by King Charles III of Spain in 1785. Pope Leo XIII made UST a pontifical university in 1902. Pope Pius XII bestowed the title of The Catholic University of the Philippines in 1947. The university houses the first and oldest engineering, law, medical, and pharmacy schools in the country. The main campus is the largest university in the city of Manila and is home to 22 degree-granting colleges, a parish church, and a teaching hospital. The National Museum of the Philippines declared four of the university's structures and the UST Baybayin Documents as National Cultural Treasures.

The university offers programs in over 180 undergraduate and graduate specializations. It has 26 programs recognized by the Commission on Higher Education (CHED) as Centers of Excellence and Centers of Development. It is awarded institutional accreditation by the CHED through the Federation of Accrediting Agencies of the Philippines (FAAP). The university has the highest number of Philippine Association of Colleges and Universities' Commission on Accreditation (PACUCOA)-accredited programs in the country, with 59.

UST alumni and faculty include 30 Catholic saints, four presidents of the Philippines, 17 senators, nine chief justices, 20 national artists, a national scientist, and five billionaires. The athletic teams are the Growling Tigers, who are members of the University Athletic Association of the Philippines and have won the overall championships more than any other university.