or BIRR, a market-town of Ireland, in King's County, stands on a gentle slope near the Little Brosna, 22 miles S.W. of Tullamore, and 69 W.S.W. of Dublin. It is separated into two parts by the Birr, a small affluent of the Little Brosna; and it consists of one chief and several smaller streets. They are generally straight and clean, and are lined with well-built stone houses. At one end of the principal street is a handsome square, containing a column and statue of the Duke of Cumberland, erected in 1747 to commemorate the battle of Culloden. The parish church, built in 1815, is a fine Gothic edifice with a square tower. The only other remarkable building is a Roman Catholic church surmounted with a lofty spire. There are several other places of worship, a courthouse, several schools, a reading-room, public library, savings-bank, dispensary, fever hospital, workhouse, and bridewell. In Parsonstown and its vicinity there are flour and rape mills, linen factories, breweries, and distilleries. Corn markets are held weekly, and fairs quarterly. The trade, however, is of little importance. Close upon the town stands Birr Castle, the seat of the Earl of Rosse. It is a fine castellated and embattled building of great antiquity; but it has been considerably modernized. In the lawn in front of the castle Lord Rosse's great telescope has been set up. Pop. (1852) 5540.