Biševo (Italian: Busi ) is an island in the Croatian part of the Adriatic Sea.
It is situated in the middle of the Dalmatian archipelago, five kilometers southwest of the Island of Vis.
Its area is 5.8 km2, and it has a population of 19 (as of 2001). It is composed of limestone; the highest point is Straženica, 239m high.
In the center of the island there is a fertile field, the northern part of the island is covered with pine forests and the rest of the island is covered with maquis shrubland or bare rocks.
The coastal sea belt is a rich fishing area. The main industries are viticulture and fishing.
A Benedictine monastery was founded on Biševo in 1050 by Ivan Grlić from Split, but it was deserted two centuries later because of the danger of pirates. The church of Saint Sylvester is preserved near the ruins of the monastery.
On the steep shores there are many caves, the most famous being the Blue Cave. It has been accessible since 1884, and approach is possible only by boat.
It is 18 meters long, 6 meters deep and 6 meters high.
The entrance to the cave is only 1.5 meters high and 2.5 meters wide.
Around 10 to 13 o'clock sunbeams that penetrate through the submarine opening in the Blue Cave, reflect from the white bottom floor and colour the cave in blue and objects in the water in silver.