thumb|Camilla threatens Lothario with a sword. Illustration by , engraving by [[Francisco Fusté.|alt=A man raises a hand to stop a woman with a long dagger.]]
Lothario is an Italian name used as shorthand for an unscrupulous seducer of women, based upon a character in The Fair Penitent, a 1703 tragedy by Nicholas Rowe. In Rowe's play, Lothario is a libertine who seduces and betrays Calista; and his success is the source for the proverbial nature of the name in the subsequent English culture. The Fair Penitent itself was an adaptation of The Fatal Dowry (1632), a play by Philip Massinger and Nathan Field. The name Lothario was previously used for a somewhat similar character in The Cruel Brother (1630) by William Davenant.
It was first mentioned in the modern sense in 1756 in The World, the 18th century London weekly newspaper, No. 202 ("The gay [meaning joyful, merry] Lothario dresses for the fight"). Samuel Richardson used "haughty, gallant, gay Lothario" as the model for the self-indulgent Robert Lovelace in his novel Clarissa (1748), and Calista suggested the character of Clarissa Harlowe. Anthony Trollope in Barchester Towers (1857) wrote of "the elegant fluency of a practised Lothario".
Because of the allusive use the name sometimes is not capitalised.