The River Bush (from the Irish: an Bhuais) is an Ulster river in County Antrim, Northern Ireland. The River Bush is 33.5 miles (53.9 km) long. The river's source is in the Antrim Hills at 480m. From there the river flows northwest, with a bend at the town of Armoy. It then flows west, passing through Stranocum, and then bends north, passing through Bushmills before reaching the sea at Portballintrae on the North Antrim coast. It flows through a fertile valley devoted to grassland-based agriculture with limited arable cropping. The underlying geology is basalt and the water is slightly alkaline with magnesium making an unusually large contribution to total hardness. The river supports indigenous stocks of Atlantic salmon and brown trout.