Torsa (occasionally Torsay) is one of the Slate Islands in Argyll and Bute, Scotland. Lying east of Luing and south of Seil, the island was inhabited until the 1960s. There is now only one house on the island, which is used for holiday lets. Its main industry is farming, with cattle brought over from the neighbouring island of Luing. The Luing cattle were bred for their hardiness.
The island is connected to its smaller partner, Torsa Beag (Gaelic for little Torsa). In the bay beyond is a suspected crannog.
The island is best known for the ruined sixteenth-century hunting lodge Caisteal nan Con. This is known locally as the Castle of the Dogs. It is doubtful that the castle would have originally been built as a hunting lodge, as it is in a very fine defensive position built upon a sheer rocky outcrop overlooking the sea on three sides. However, over time this may have become the final use of the building before falling into disrepair.