George Peacock was born 9 April 1791 in Denton, near Darlington, co. Durham, one of eight children, the youngest of five sons of Thomas Peacock, curate and schoolmaster at Denton. After a short spell at Richmond School he came up to Trinity College, Cambridge in 1809, where he graduated as Second Wrangler. He was elected Fellow of Trinity in 1814, and received his MA in 1816.
In 1815 Peacock was appointed a Mathematics lecturer at Trinity, and became a tutor in 1823. His leanings towards reform were exercised in his review of the Mathematics Tripos during his three spells as moderator, from 1816 to 1821, as well as work on committees to rebuild the University Library and build the Fitzwilliam Museum, amongst other projects. He was elected a fellow of the Royal Society in 1818, and was given the Lowndean professorship of astronomy and geometry in 1837, a position he held until his death. He lectured for many years on mathematical theory in this role, and was on the committee in 1843 to restore the standards of weights and measures which had been destroyed in the parliament building fire.
Peacock was appointed Dean of Ely in 1839 and turned over the astronomy lectures to the Plumian professor of astronomy and experimental philosophy, retaining the Lowndean chair as a sinecure for the rest of his life. In Ely he persuaded the chapter to restore the cathedral, improved education for the middle and lower classes, and improved the city's drainage system. In 1841 Peacock published 'Observations on the Statutes of the University of Cambridge', advocating academic and political reform of the university and colleges, and served on the royal commission for inquiry at Cambridge in 1850, and and to a royal statutory commission for Cambridge in 1855.He was able to initiate many reforms, despite the opposition of Trinity master William Whewell.
He married Frances Elizabeth, daughter of William Selwyn, in 1847, and died at Ely in November 1858.