Don (Spanish: [don], Italian: [dɔn], Portuguese: Dom [dõ], from Latin dominus, roughly 'Lord'), abbreviated as D., is an honorific title used in Spain, Portugal, Italy, Iberoamerica and the Philippines.
The female equivalent is Doña (Spanish: [ˈdoɲa]), Donna (Italian: [ˈdɔnna]), and Dona (Portuguese: [ˈdonɐ]), abbreviated Dª, Da., or simply D.
Although originally a title reserved for royalty, select nobles, and church hierarchs, it is now often used as a mark of esteem for a person of personal, social or official distinction, such as a community leader of long standing, a person of significant wealth, or a noble, but may also be used ironically. As a style, rather than a title or rank, it is used with, and not instead of, a person's name.
Syntactically, it is used in much the same way (although for a broader group of persons) as "Sir" and "Dame" are used in English when speaking of or to a person who has been knighted, e.g. "Don Firstname" or "Doña Firstname Lastname". Unlike "The Honourable" in English, Don may be used when speaking directly to a person, and unlike "Mister" it must be used with a given name. For example, "Don Diego de la Vega," or (abbreviating "señor") "Sr. Don Diego de la Vega," or simply "Don Diego" (the secret identity of Zorro) are typical forms. But a form like "Don de la Vega" is not correct and would never be used by Spanish speakers. "Señor de la Vega" should be used instead.