The Strei is a left tributary of the river Mureș in Transylvania, Romania. It starts at the confluence of headwaters Pârâul Cald and Pârâul Rovinei. The upper reach of the river, upstream of the village of Baru is also known as Râul Petros. It flows through the town Călan and the villages Petros, Baru, Livadia, Pui, Galați, Băiești, Ohaba de sub Piatră, Ciopeia, Subcetate, Covragiu, Bretea Română, Bretea Streiului, Ruși, Strei, Streisângeorgiu, Batiz, Băcia and Simeria Veche. It discharges into the Mureș near Simeria.