The Great Western Greenway (Irish: Bealach Mór an Iarthair) is a greenway rail trail in County Mayo, Ireland.
It is 42 kilometres (26 miles) long and begins in Westport and ends in Achill, passing through the towns of Newport and Mulranny as it runs along the coast of Clew Bay. It is an off-road trail intended for use by cyclists and walkers. It follows the route of the former Achill extension of the Westport railway line, which was constructed in the 1890s and closed in 1937. An estimated 300 people cycle and walk the trail each day, which was constructed at a cost of €3 million. The first section, from Newport to Mulranny, was opened in April 2010. It was named as the 2011 Irish winner of the European Destinations of Excellence award. The full route was opened by TaoiseachEnda Kenny, T. D. and Minister of State for Tourism and Sport, Michael Ring, T. D., on 29 July 2011.