Literally is an English adverb meaning "in a literal sense or manner" or an intensifier which strengthens the associated statement. It has been used as an intensifier in English for several centuries, though since the early 20th century it has been considered somewhat controversial by linguistic prescriptivists. The use of 'literally' as an intensifier is recognized as valid by most dictionaries of English and has been used by authors such as Mark Twain and James Joyce.

The first known use of the word literally was in the 15th century, or the 1530s.

The use of the word as an intensifier emerged later, at the latest by 1769, when Frances Brooke wrote the following sentence:

He is a fortunate man to be introduced to such a party of fine women at his arrival; it is literally to feed among the lilies.

— Frances Brooke, The History of Emily Montague

Despite common perception to the contrary, the use of an intensifier does not mean "figuratively" and is not an auto-antonym; literally as an intensifier cannot be lexically substituted for figuratively while keeping the meaning of the sentence the same, and instead it serves as a generic intensifier. Its use as an intensifier dates back to the 1700s, and only since the early 20th century has its use as an intensifier been controversial. In 1909, the following entry was included in a blacklist of literary faults:

Literally for Figuratively. "The stream was literally alive with fish." "His eloquence literally swept the audience from its feet." It is bad enough to exaggerate, but to affirm the truth of the exaggeration is intolerable.

— Ambrose Bierce, Write it Right: A Little Blacklist of Literary Faults