Cecil Edgar Tilley FRS (14 May 1894 – 24 January 1973) was an Australian-British petrologist and geologist.
He was born in Unley, Adelaide, the youngest child of John Thomas Edward Tilley, a civil engineer from London, and his wife South Australia-born wife Catherine Jane (née Nicholas). He was educated at Adelaide High School, then studied under William Rowan Browne at the University of Adelaide, and the University of Sydney. He went to England to work in the munitions industry during World War I but returned after the Armistice.
He won an Exhibition of 1851 scholarship to the University of Cambridge in 1919 where he studied under Alfred Harker. Most of the remainder of his career was spent in England, though spent 1938-9 in Australia and visited regularly after the War.
In 1929, while investigating a volcanic plug at Scawt Hill, near Larne, Northern Ireland for the Mineralogical Magazine he identified and named the new minerals larnite and scawtite.
In 1931 he was appointed professor of Mineralogy and Petrology at Trinity Hall, Cambridge, a newly created department.