Ballinasloe, town, County Galway, Ireland, on the River Suck and a northerly extension of the Grand Canal. Originally a small settlement beside the medieval castle guarding the important Suck crossing, the town was developed mainly in the 18th century. It is the main market town of east County Galway and is noted for its livestock fairs, the largest in Ireland, which reached a peak in the mid-19th century. The famous local quarries supplied the masonry for a street of shop fronts in New York City. It is also an important angling centre. Pop. (2002) 5,984; (2011) 6,449.