Newnham College is a women's college in the University of Cambridge. It was founded in 1872 by Henry Sidgwick and was the second Cambridge college to admit women, the first being Girton. It started life as a small house on Regent Street, housing 5 female students who wished to attend lectures but did not live near enough to the university to do so (the university allowed women to attend lectures from 1870). In 1875 the first building was built on the current site on Sidgwick Avenue, now called Old Hall. The college continued to grow and three more buildings were constructed. These buildings (and others built later) are grouped around some of the most attractive gardens in Cambridge, cunningly hidden from the road by the buildings that surround them. Not only are they lovely gardens, but (unlike most of Cambridge's colleges) all residents can walk on the grass for most of the year. Newnham also had laboratories because women were not permitted into the university labs. These now house a drama space and a library. This library was originally Newnham students' primary reference source since women were not allowed into the University Library. It remains one of the largest college libraries in Cambridge.

Newnham taught a varied curriculum, tailored to the students who generally had far less formal education than their male counterparts (unlike Girton which accepted women on the same terms, and taught them the same curriculum as men in the other colleges). Although it was usual for a male student to take his degree after three years of study, not all Newnham students completed an entire degree course after four years' work.

Women were not generally permitted to take examinations in the university until 1881 and were not admitted to degrees (previously they were awarded only a certificate from their college) until 1921, a year after their counterparts at Oxford. It was not until 1958 that women were granted full rights as members of the university.

In 1954, a third women's college, New Hall, was founded. Wolfson was the first mixed college and was founded in 1965. 1972 saw three men's colleges (Churchill, Clare and King's) admit women for the first time. Cambridge now has no all-male colleges and Girton is also mixed, although both Newnham and New Hall remain all-female.

Alumnae of Newnham include:

• Germaine Greer
• Sylvia Plath
• Emma Thompson
• Margaret Drabble
• Diane Abbott
• Patricia Hewitt
• Rosalind Franklin

In 1928, Newnham, along with Girton College was one of the venues for a series of lectures by Virginia Woolf that resulted in the famous book-length essay A Room of One's Own.

Newnham College was the clear conceptual and architectural inspiration for University Women's College at the University of Melbourne, Australia (now University College).