Sir Philip Montefiore Magnus-Allcroft, 2nd Baronet, CBE (8 February 1906 – 21 December 1988), was a British biographer.
Magnus-Allcroft was born in London, the son of Laurie Magnus and Dora Marian Spielmann, the grandson of the educationalist and Conservative politician Sir Philip Magnus, 1st Baronet. He was a member of a notable Jewish family; his paternal grandmother was the historian Katie Emmanuel and his maternal grandmother was Emily Sebag-Montefiore.
Magnus succeeded to the title of 2nd Baronet Magnus in 1933.
During the Second World War he was a Captain in the Royal Artillery and Army Intelligence Corps, rising to the rank of Major. He married Jewell Allcroft in 1943, and in 1951 added the name of Allcroft to his own by deed poll.
In later years, as well as writing, he served as a Justice of the Peace, Shropshire County Councillor, chairman its planning committee and the records committee, chairman of the governors of Attingham College and governor of Ludlow grammar school. Between 1970 and 1977 he was a trustee of the National Portrait Gallery. He lived in Stokesay Court, Shropshire, England.