Peter John Wyllie (born 8 February 1930, in London, England) is a British petrologist and academic.
He was Professor of Geology at the California Institute of Technology from 1983 until his retirement in 1999.
[1] He is well known for his many contributions to the understanding of magmatism, particularly through his work on the experimental petrology of magmas and volatiles.
[2] He is also famous for his contributions to the coverage of earth sciences in the Encyclopædia Britannica, particularly his outline of the field in Part Two of the Propædia.
Wyllie was President of the International Union of Geodesy and Geophysics (IUGG) from 1995 to 1999.