An aviso was originally a kind of dispatch boat or "advice boat", carrying orders before the development of effective remote communication.
The term, derived from the Portuguese and Spanish word for "advice", "notice" or "warning", an adviso, was later adopted by the French and Portuguese navies to classify their medium-sized warships designed for colonial service. The term continued to be used in the French Navy to classify the D'Estienne d'Orves-class patrol frigates until 2012, when the remaining ships of the class were reclassified as offshore patrol ships. It is equivalent to the modern use of "sloop" in other countries.
The Dictionnaire de la Marine Française 1788–1792 (by Nicolas-Charles Romme) describes avisos as "small boats designed to carry orders or dispatches". This use became obsolete with the development of means of communicating detailed information at a distance.
French avisos used during World War I and World War II had displacements of 300–700 tons, speeds of 13–20 knots (24–37 km/h; 15–23 mph), main armaments usually of two 100 mm guns, two 138 mm guns, or four 100 mm guns. Colonial avisos, such as the Bougainville class intended for overseas service, were larger.
The Portuguese Navy used avisos to operate in the waters of the Portuguese Empire. The Portuguese built the 1st rate Afonso de Albuquerque class of 1,780 tons and the 2nd rate (Gonçalo Velho and Pedro Nunes classes of 950 to 1,090 tons).
In some navies the term is now used to include combat-capable ships larger than patrol boats, but smaller than corvettes. They typically have roles in anti-submarine warfare and coastal defence. In NATO classification they are usually recognized as corvettes.
The Argentine Navy has several ships classified as avisos. ARA Alferez Sobral, an 800-ton vessel used for non-combat tasks, built as a US Navy fleet tug, was attacked and damaged during the 1982 Falklands War.