Caher (or Cahir), a market-town of Co. Tipperary, Ireland, in the south parliamentary division, beautifully situated on the river Suir at the foot of the Galtee Mountains. Pop. (1901) 2058. It stands midway between Clonmel and Tipperary town on the Waterford and Limerick line of the Great Southern and Western railway, 124 m. S.W. from Dublin. It is the centre of a rich agricultural district, and there is some industry in flour-milling. Its name (cathair, stone fortress) implies a high antiquity and the site of the castle, picturesquely placed on an island in the river, was occupied from very early times. Here was a fortress-palace of Munster, originally called Dun-iasgach, the suffix signifying "abounding in fish." The present castle dates from 1142, being built by O'Connor, lord of Thomond, and is well restored. It was besieged during the wars of 1599 and 1647, and by Cromwell. Among the fine environs of the town the demesne of Caher Park is especially noteworthy. The Mitchelstown stalactite caverns, 10 m.
S.W., and the finely-placed Norman castle of Ardfinnan, on a precipitous crag 6 m. down the Suir, are other neighbouring features of interest, while the Galtee Mountains, reaching in Galtymore a height of 3015 ft., command admirable prospects.