Leinster, one of the four provinces of Ireland, constituting; the S. E. part of the island, between lat. 52° 7' and 54° 6' N., and Ion. 6° and 8° 3' W., bounded N. by Ulster, E. by St. George's channel, S. by the Irish sea, and W. by Munster and Connaught; length N. and S., 132 m.; greatest breadth, 82 m.; area, 7,553 sq. m.; pop. in 1871, 1,335,966' (in 1841, 1,973,731). It is divided into 12 counties: Carlow, Dublin, Kildare, Kilkenny, King's, Longford, Louth, Meath, Queen's, Westmeath, Wexford, and Wicklow, besides the cities of Dublin and Kilkenny, and the town of Drog-lieda, which are counties in themselves. The coast is generally low, but in some places bold and rocky. The best harbors are at Dublin, Drogheda, Dundalk, and Carlingford. There are no large lakes. The province contains six navigable rivers, the Shannon, Barrow, Nore, Boyne, Liffey, and Slaney. The surface is partly level and partly rolling, being on the whole the least broken portion of Ireland. There are three or four mountain groups occupying parts of Dublin, Wicklow, Carlow, Wexford, Queen's, and King's counties, and a few hills in Westmeath, Louth, and Kilkenny. Elsewhere are large peat fields, the principal of which is the great bog of Allen. The soil, resting on limestone and clay slate, is the best in the kingdom.

The Kilkenny coal field, between the Barrow and Nore, is the most extensively worked in Ireland, and also produces excellent ironstone. Wicklow has five copper and four lead mines, yielding silver, and in Croghan there is a gold mine, now abandoned. At the time of the Anglo-Norman invasion in the 12th century Leinster was divided into two kingdoms, Meath in the north and Lega-nia or Leinster proper in the south.