Independent Senator David Norris will retire from politics in January.
He told the Trinity News that he intends to move to Cyprus to enjoy some sunshine.
Senator Norris said it was time to pass the "baton to the next generation".
He will formally announce his retirement from the Seanad when the upper house returns after the Christmas recess.
Mr Norris has been a member of Seanad Éireann since 1987.
He unsuccessfully contested the presidential election in 2011.
Fianna Fáil Senator and Spokesperson on Higher Education Malcolm Byrne said Mr Norris has made an outstanding contribution to Irish public life in so many ways.
He said: "He will be most associated, however, with the campaign for LGBT rights.
"In a way that personally benefitted me, David's campaigning for the decriminalisation of homosexuality and for the greater participation of LGBT persons in Irish society, including through marriage equality, truly made a difference in the lives of so many."
Cathaoirleach of the Seanad Jerry Buttimer said Mr Norris had left a huge legacy during his 36 years in the house.
"My life and that of the LGBTQ community is all the better because of your bravery courage and determination," he said.
