A Lothario is a man who commonly seduces women, or who is viewed as intensely attractive to women, even if he chooses not to pursue them. As a general rule, Lotharios are also viewed as somewhat dangerous, since the assumption is that after the seduction, they will throw the woman away. Some similar slang terms include “Casanova” and “Don Juan.” Curiously enough, no female counterpart to Lothario exists, at least in English, perhaps because of a double-standard about sexual behavior which dominates many English-speaking societies.
This slang term is a reference to a play called The Fair Penitent, written by Nicholas Rowe and published in 1703. In the play, Lothario is a character who seduces a woman and then ultimately betrays her. Rowe may have borrowed the character from Don Quixote (1605), where a remarkably similar situation also includes a character named Lothario. By the 1750s, “Lothario” had entered common English slang to refer to a seducer, usually with the implication that the seduction would inevitably end in betrayal of some form or another.
Men are often accused of being Lotharios if they are flirtatious with women, especially if they are attractive. While such men might protest that the flirting rarely, if ever, progresses into anything more serious, they are still viewed as seducers, especially if they happen to be flirting with other people's wives. For young single men, being a Lothario can be a status symbol in some cultures, since men are commonly expected to be adventurous in their youths.
The concept of the Lothario has probably endured for so long in English slang because people can readily identify with it, and because it comes up again and again in poetry, fiction, and film. Lotharios are a dime a dozen in romance novels, cause the female leads to swoon in comic and tragic plays, and they fill the screen in soap operas. Even if such men are comparatively rare, their frequent appearances in materials designed for entertainment ensures that they are kept in the forefront of the mind.
Some people view the stereotype of the Lothario as harmful, because they believe that it reinforces sexist double-standards, and because it sometimes prejudices people against handsome and flirtatious men. Such men may be perfectly nice individuals who have no intention of abandoning the objects of their affection, but people may believe that they are “too beautiful” to be serious.