Charlestown (Irish: Baile Chathail), once named Newtown-Dillon or Ballycattell, is a town in the Barony of Costello, County Mayo, Ireland. It is located at the intersection of two National Primary routes, the N17 and the N5. Until the N5 bypass opened in November 2007, traffic congestion was a problem in the town. The busy N17 still passes through the town.