The University of London (UoL; abbreviated as Lond or more rarely Londin in post-nominals) is a federal public research university located in London, England, United Kingdom. The university was established by royal charter in 1836 as a degree-awarding examination board for students holding certificates from University College London and King's College London and "other such other Institutions, corporate or unincorporated, as shall be established for the purpose of Education, whether within the Metropolis or elsewhere within our United Kingdom". This fact allows it to be one of three institutions to claim the title of the third-oldest university in England, and moved to a federal structure in 1900. It is now incorporated by its fourth (1863) royal charter and governed by the University of London Act 2018.

It was the first university in the United Kingdom to introduce examinations for women, in 1869 and, a decade later, the first to admit women to degrees. In 1913, it appointed Caroline Spurgeon as only the second female professor at a British university, and in 1948 was the first British university to appoint a woman as its vice chancellor (chief executive). The university's member institutions house the oldest teaching hospitals in England.

The university consists of 17 member institutions and three central academic bodies The university has around 48,000 distance learning external students and around 219,410 campus-based internal students, making it the largest university by number of students in the United Kingdom. For most practical purposes, ranging from admissions to funding, the member institutions operate on an independent basis, with many awarding their own degrees whilst remaining in the federal university.

The largest colleges by enrolment are UCL, King's College London, City, Queen Mary, Birkbeck, the London School of Economics, Royal Holloway, and Goldsmiths, each of which has over 9,000 students. Smaller, more specialist, colleges are the School of Oriental and African Studies (SOAS), St George's (medicine), the Royal Veterinary College, London Business School, the London School of Hygiene and Tropical Medicine, the Royal Central School of Speech and Drama, the Royal Academy of Music, the Courtauld Institute of Art, and the Institute of Cancer Research. Imperial College London was a member from 1908 until it became an independent university in 2008, and Heythrop College was a member from 1970 until its closure in 2018. City is the most recent constituent college, having joined on 1 September 2016.

Under the 2018 Act, member institutions ceased to be termed colleges and gained the right to seek university status without having to leave the federal university: Birkbeck, City, Goldsmiths’, King's College London, the LSE, the London School of Hygiene and Tropical Medicine, Queen Mary, the Royal Veterinary College, Royal Holloway, SOAS, St George's and UCL have all indicated that they intend to do so.

As of 2015, there are around 2 million University of London alumni across the world, including at least 14 monarchs or royalty, more than 60 presidents or prime ministers in the world (including 5 prime ministers of the United Kingdom), 2 Cabinet Secretaries of UK, 85 Nobel laureates, 5 Fields Medallists, 4 Turing Award winners, 6 Grammy winners, 2 Oscar winners, 3 Olympic gold medalists and the "Father of the Nation" of several countries. The university owns University of London Press.