Cambridge University Library is the main research library of the University of Cambridge. It is the largest of over 100 libraries within the university. The library is a major scholarly resource for members of the University of Cambridge and external researchers. It is often referred to within the university as the UL. Thirty-three faculty and departmental libraries are associated with the University Library for the purpose of central governance and administration, forming "Cambridge University Libraries".

Cambridge University Library is one of six legal deposit libraries under UK law. It holds about 9 million items (including maps and sheet music) and, through legal deposit, purchase and donation it receives around 100,000 items every year. The University Library is unique among the legal deposit libraries in keeping a large proportion of its material on open access and in allowing some categories of reader to borrow from its collections.

Its original location was the Old Schools near the Senate House until it outgrew the space there. A new library building was constructed in the 1930s. The library took over the site of a former military hospital on the western side of Cambridge city centre, now between Robinson College and the Memorial Court of Clare College. The current building, designed by Giles Gilbert Scott, opened in 1934. The librarian, Jessica Gardner, is the second woman to hold this office.