Osasio ( Osas Piedmontese ) is a municipality with 936 inhabitants (as at 31 December 2012) in the Italian province of Turin (TO ), Region Piedmont.
The neighboring municipalities are castagnole Piemonte, Piemonte Virle, Carignano, Pancalieri and Lombriasco.
The municipality covers an area of 4 km ².
Osasio, originally Olsazio is, since the 12th century known as a fief of the Sacra di San Michele in Val di Susa. It was located on the border between the county of Savoy and the Margraviate of Saluzzo. The Po formed this limit. So changed over the centuries include membership of Osasio between these two territories. In the 19th century Osasio came by inheritance in the female line to the counts Verrua of it to the Marquis Amoretti from Envie. From 1928 belonged to the municipality for 18 years Osasio Pancalieri; since 1946, it is an unincorporated community again.