County Dublin was a parliamentary constituency in Ireland, which returned two Members of Parliament (MPs) to the House of Commons of the Parliament of the United Kingdom.

The constituency was created under the Acts of Union 1800, replacing the constituency of County Dublin in the Irish House of Commons. Under the Redistribution of Seats Act 1885, before the 1885 general election, it was replaced with two new county divisions, South Dublin and North Dublin.

This constituency comprised the whole of County Dublin, except for the area of the borough constituency of Dublin City. The borough comprised the whole of the county of the city of Dublin and the portion of the county at large within the Circular Road.

A Topographical Directory of Ireland, published in 1837, describes some aspects of the Parliamentary history of the county.

Two knights of the shire are returned to the Imperial parliament, who are elected at the county court-house at Kilmainham : the number of electors registered under the 2d of William IV., c. 88, up to Feb. 1st, 1837, is 2728, of which 788 were £50, 407 £20, and 622 £10, freeholders; 18 £50, 427 £20, and 423 £10, leaseholders; and 12 £50, 30 £20, and 1 £10, rent-chargers : the number that voted at the last general election was 1480. Prior to the Union, the boroughs of Swords and Newcastle sent each two members to the Irish House of Commons.