in the House of Commons of the United Kingdom of Great Britain and Ireland as member of the Irish Parliamentary Party, from 1910 the All-for Ireland Party, who represented the West Cork constituency from 1885 for 30 years until his death, retaining his seat in eight elections (four of them contested).
He died on 16 October 1916 at Madame Goulding's Private Hospital, Patrick's Place, Cork and was buried at Abbey Cemetery, Bantry, the town closing down for his funeral and many houses showed black crepe.
The ensuing bitter West-Cork by-election has a place in history as the first after the Rising and the last in which the Irish Party narrowly captured a seat and as the self-induced demise of the AFIL.
In November three candidates were nominated, the third also a local AFIL supporter and member who stood in protest after O’Brien had passed him over in favour of a Sinn Féin close candidate (Frank Healy), thereby splitting the AFIL vote to the detriment of O’Brien's party.
[1] (At that time seats were won by "candidates first past the post", or uncontested as in 1918 by Michael Collins of Sinn Féin)