Sir William Hunter McCrea (13 December 1904 – 25 April 1999[1][2]) was an English astronomer and mathematician.

He went to Trinity College, Cambridge in 1923 where he studied Mathematics, later gaining a PhD in 1929 under Ralph H. Fowler.

After the war, he joined the mathematics department at Royal Holloway College where he remained a professor for twenty years.

In 1965, McCrea created the astronomy centre of the physics department at the University of Sussex.

In 1928, he studied Albrecht Unsöld's hypothesis, and discovered that three-quarters of the Sun is made of hydrogen, and about one quarter is helium, with 1% being other elements.