Charles Talbut Onions (C.T. Onions) (1873-1965) was an English grammarian and lexicographer.

He joined James Murray on the staff of the Oxford English Dictionary at Oxford in 1895 and in 1914 he began independent editorial work with his own assistants. His A Shakespeare Glossary was published in 1911. He co-edited the 1933 Supplement with William Craigie. Following the death of William Little in 1922, he assumed the editorship of the Shorter Oxford English Dictionary. His last work is The Oxford Dictionary of English Etymology (1966), which was published posthumously and is generally considered to be the standard work on the subject.

Born in Edgbaston, (now in the West Midlands), he received his M.A. at the University of London and an honorary doctorate from Oxford. He was a fellow and librarian of Magdalen College, Oxford and a corresponding fellow of the Medieval Academy of America . He was editor of the journal Mediam Aevum from 1932 to 1956.