In 1836, King's became one of the two founding colleges of the University of London. In the late 20th century, King's grew through a series of mergers, including with Queen Elizabeth College and Chelsea College of Science and Technology (in 1985), the Institute of Psychiatry (in 1997), the United Medical and Dental Schools of Guy's and St Thomas' Hospitals and the Florence Nightingale School of Nursing and Midwifery (in 1998).
King's has five campuses: its historic Strand Campus in central London, three other Thames-side campuses (Guy's, St Thomas' and Waterloo) nearby and one in Denmark Hill in south London. It also has a presence in Shrivenham for its professional military education and in Newquay, Cornwall, where its information service centre is based. In 2019/20, King's had a total income of £964.3 million, of which £200.5 million was from research grants and contracts. It has the fourth-largest endowment of any university in the United Kingdom and the largest of any in London. It is the 12th largest university in the United Kingdom by total enrolment. Its academic activities are organized into nine faculties, which are subdivided into numerous departments, centers, and research divisions.

It is a member of academic organizations including the Association of Commonwealth Universities, the European University Association, and the Russell Group. King's is home to six Medical Research Council centers and is a founding member of the King's Health Partners academic health sciences center, Francis Crick Institute and MedCity. It is the largest European centre for graduate and post-graduate medical teaching and biomedical research, by the number of students, and includes the world's first nursing school, the Florence Nightingale Faculty of Nursing and Midwifery. King's is at times regarded as part of the "golden triangle" of universities located in the cities of Oxford, Cambridge, and London.

King's alumni and staff include 14 Nobel laureates; contributors to the discovery of DNA structure, Hepatitis C, and the Higgs boson; pioneers of in-vitro fertilization, stem cell/mammal cloning, and the modern hospice movement; and key researchers advancing radar, radio, television, and mobile phones. Alumni also include heads of states, governments, and intergovernmental organizations; nineteen members of the current House of Commons and seventeen members of the current House of Lords; and the recipients of three Oscars, three Grammys, and one Emmy.

King's enjoys royal patronage by virtue of its foundation.