Sir John Knewstub Maurice Rothenstein(11 July 1901 – 27 February 1992) was a British arts administrator and art historian.
John Rothenstein was born in London in 1901, the son of Sir William Rothenstein. The family was connected to the Bloomsbury Set. John Rothenstein studied at Worcester College, Oxford, and became friends with T. E. Lawrence. He shared rooms with novelist William Gerhardie.
After serving as Director of Leeds City Art Gallery, he was appointed Director of Sheffield City Art Galleries (1932-38) where he oversaw the establishment and opening of the Graves Art Gallery. From 1938–64 Rothenstein was Director of the Tate Gallery in London. Rothenstein's directorship — the longest to date — was one of the most successful. The Tate's annual purchase fund could not compete with those of US institutions, so few works of modern foreign art were added to the collection. However, he wrote, "Picasso is a Proteus, the prodigiously gifted master of all styles and media".
According to Richard Cork, one of Rothenstein's errors was failing to purchase Henri Matisse's The Red Studio when it was offered to the Tate Gallery for a few hundred pounds in 1941.
Art historian Douglas Cooper began an open campaign to have Rothenstein dismissed by the trustees; which led to an incident in which Rothenstein punched Cooper in the face.
Rothenstein documented the lives of all the major (and many still overlooked) British artists in his Modern English Painters, which has earned him the title of 'The Vasari of British Art' (like Vasari's pioneering Lives, it was revised and reprinted within the author's lifetime).
The Tate began hosting temporary exhibitions during this period, organised by the Arts Council of Great Britain, including the major 1960 retrospective of Picasso. Rothenstein acquired such contemporary works as R.B. Kitaj's Isaac Babel Riding with Budyonny from the artist's first major show at Marlborough Fine Art in 1963.
An annual lecture named in his honour now takes place at Tate Britain.
Rothenstein was appointed Commander of the Order of the British Empire (CBE) in the 1948 King's Birthday Honours, and knighted in the 1952 New Year Honours.
On 19 February 1965 he was installed as the Rector of the University of St Andrews and received an honorary Doctor of Laws.