County Mayo 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.
The elections in this constituency took place using the first past the post electoral system.
[citation needed] Browne was elevated to the peerage, becoming 1st Baron Oranmore and causing a by-election.
Blake resigned by accepting the office of Steward of the Chiltern Hundreds, causing a by-election.
Parnell was also elected MP for Cork City and opted to sit there, causing a by-election.