William John Greenstreet (1861–1930) was an English mathematician who was editor of The Mathematical Gazette for more than thirty years.

[1] Greenstreet was son of a Royal Artillery's Sergeant.

He was educated at Southwark and he entered St John's College, Cambridge in 1879, graduating there in 1883.

In 1910 he retired to Burghfield Common with the intention of devoting to literary work.

[2] Greenstreet was founding member of the Mathematical Association[dubious – discuss] and he started the Association's Library given a large collection of books.