Sire is an archaic respectful form of address to reigning kings in Europe. In French and other languages it is less archaic and relatively more current.^{[citation needed]} In Belgium, the king is addressed as "Sire..." in both Dutch and French.^{[citation needed]}

The words "sire" and "sir", as well as the French "(mon)sieur", the Spanish "señor", and the Portuguese "senhor", share a common etymological origin, all ultimately being related to the Latin senior. The female equivalent form of address is dame or dam.