Lastovo (lâstɔv̞ɔ; Lagosta, Augusta, Augusta Insula, Ladestanos, Illyrian: Ladest) is an island municipality in the Dubrovnik-Neretva County in Croatia. The municipality consists of 46 islands with a total population of 792 people, of which 94,7% are ethnic Croats, and a land area of approximately . The biggest island in the municipality is also named Lastovo, as is the largest town. The majority of the population lives on the island of Lastovo.
Lastovo, like the rest of the Roman province of Dalmatia, was settled by Illyrians. The Romans conquered and settled the entire area, retaining control until the Avar invasions and Slavic migrations in the 7th century. The Croats and other Slavic tribes subjugated by the Croats secured most of the Dalmatian seaboard, but some cities and islands (like Lagosta) of the romanised Dalmatians remained independent under the nominal rule of the Byzantines. In 1000 AD the Venetians attacked and destroyed the settlement due to the island's participation in piracy along the Adriatic coast. After the Venetian domination, in the 13th century Lagosta joined the Republic of Ragusa where for several centuries it enjoyed a certain level of autonomy until the republic's conquest by the French, under Napoleon. Austria then ruled the island for the next century, then Italy for 30 years after World War I, and finally Yugoslavia until it became a part of the independent Republic of Croatia.
The island is noted for its 15th- and 16th-century Venetian architecture. There is a large number of churches of relatively small size, a testament to the island's long-standing Roman Catholic tradition. The major cultural event is the Poklade, or carnival. The island largely relies on its natural environment to attract tourists each season. In 2006 the Croatian Government made the island and its archipelago a nature park.
The island of Lastovo belongs to the central Dalmatian archipelago. Thirteen kilometres () south of Korčula, the island is one of the most remote inhabited islands in the Adriatic Sea.