ATHY (pronounced Athy)  , a market-town of Co . Kildare, Ireland, in the south parliamentary division, 45 M . S.W. of Dublin on a branch of the Great Southern & Western railway . Pop. of urban district (19o1) 3599 . It is intersected by the river Barrow, which is here crossed by a bridge of five arches . The crossing of the river here was guarded and disputed from the earliest times, and', the name of the town is derived from a king of Munster killed here in the 2nd century . There are picturesque remains of Woodstock Castle of the 12th or 13th century, and White Castle built in 15o6, and rebuilt in 1575 by a member of the family whose name it bears, and still occupied . Both were erected to defend the ford of the Barrow . There are also an old town gate, and an ancient cemetery with slight monastic remains . Previous to the Union Athy returned two members to the Irish parliament . The trade, chiefly in grain, is aided by excellent water communication, by a branch of the Grand Canal to Dublin, and by the river Barrow, navigable from here to Waterford harbour .