MULLAHIDDART, or MULLAHITHART, a parish, in the barony of CASTLEKNOCK, county of DUBLIN, and province of LEINSTER, 5¾ miles (N. W. by N.) from Dublin, on the road to Navan; containing 478 inhabitants. "The guild or fraternity of the Blessed Virgin Mary," of Mullahiddart, was founded in the 23rd of Hen. VI. by act of parliament. The principal seats are Hollywood, the residence of Major Thompson; Tyrrelstown, of A. Rorke, Esq.; and Kilmartin, of J. Hoskins, Esq. The parish was formerly a northern portion of that of Castleknock. It is a rectory and curacy, in the diocese of Dublin: the rectory forms the corps of the prebend thereof in the cathedral of St. Patrick, Dublin, and in the patronage of the Archbishop; and the curacy forms part of the union of Castleknock. The tithes amount to £210, of which £70 is payable to the prebendary and the remainder to the incumbent of Castleknock. The church is in ruins, presenting, with its ivy-covered tower, a picturesque object. In the R. C. divisions the parish forms part of the union or district of Castleknock. A school under the National Board, aided by a collection at the R. C. chapel, affords instruction to 62 boys and 16 girls. A well not far from the church, dedicated to the Blessed Virgin, is frequented at certain periods by the peasantry. Ancient coins have been found near the church.