ARST S.p.A., known also as Azienda Regionale Sarda Trasporti, is a public company responsible for public transportation in Sardinia, in Italy, owned by the autonomous regional administration of Sardinia.
The company is headquartered in Cagliari and has 2,166 employees. It operates a large part of the intercity bus lines on the island (it had 175 bus lines and a network of in 2007), urban bus lines in six municipalities (Alghero, Carbonia, Iglesias, Macomer, Guspini and Oristano), commuter and urban rail transport on of narrow gauge railways and on two metrotramways operating in Sassari and Cagliari. ARST operates also of narrow railways, based on 4 lines, used as a rail tourism service, called Trenino Verde.