Longford 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 from 1801 to 1885, and one MP from 1918–1922.
This constituency comprised the whole of County Longford.
Members of Parliament
- 1585: ___ Farrell and __ Farrell 
- 1613–1615: ___ Farrell and __ Farrell 
- 1634–1635: ___ Farrell and __ Farrell 
- 1639–1649: ___ Farrell and Sir James Dillon 
Sir Thomas Fetherston died, causing a by-election.
On petition, a House of Commons Select Committee inquiry disqualified 73 votes and declared Forbes and Lefroy the winners of the election.
Viscount Forbes died, causing a by-election.
On petition, a House of Commons committee inquiry disqualified 94 votes and declared Fox the winner of the election by a majority of 1.
On petition, a House of Commons committee began an inquiry into the votes cast for Luke White, but he withdrew his candidacy after 1 vote was examined and Lefroy was declared elected on 18 April 1842 .
Blackall was appointed Lieutenant-Governor of Dominica, causing a by-election.
Fox's death caused a by-election.
White's resignation caused a by-election.
White was appointed a Lord Commissioner of the Treasury, requiring a by-election.
Greville-Nugent was created Lord Greville, causing a by-election.
On petition, Greville-Nugent was unseated.
O'Reilly was appointed Assistant Commissioner of Intermediate Education and resigned, causing a by-election.