The 63-year-old, who was ousted in 2010, had briefly returned to the political spotlight this year to help snatch victory for the "No" camp in Scotland's historic independence referendum.
But he confirmed today he would not be standing again in next May's general election as a lawmaker for the centre-left Labour party, bringing the curtain down on his stormy Westminster career.
"I'm in no doubt it's the right thing to do," he said in an address in his constituency in Kirkcaldy in Scotland, speaking in the same church where his father was a minister.
Brown will be remembered as one of Britain's shortest-serving prime ministers -- only three residents of 10 Downing Street since 1900 were in power for less time.