Speaking to the press at midday Gauck said that serving the country since he was elected president in 2012 had been an honour, but that he would not seek to win a second term in office next year.
The office of president is a largely ceremonial role in Germany. While the President has no legislative power he plays a role in setting the moral tone of the country.
Gauck has often been present in the pages of this website for meeting foreign dignitaries such as Queen Elizabeth, or most recently attending a memorial for victims of the battle of Jutland.
He has however made important moral interventions in politics over his tenure. In April 2015 he described the massacre of around 1 million Armenians by the Ottoman empire as a ‘genocide' - a precusor to last week's Bundestag resolution that has stoked tensions with Turkey.
Last year, Gauck, who made his name as a human rights activist under communism, also lashed out at xenophobic attacks in Germany on migrants and refugees, describing them as the country's "dark" side.
The 76-year-old explained that his age was the decisive factor in convincing him he should call it a day.
“I'm thankful that I am in good health," he said.
"At the same time, I am aware that the life phase between 77 and 82 is a different one than the one I am in now. I cannot guarantee that I would have the same energy and vitality for another five-year term."
He said that it had been an honour to fulfil the role of president and that he would continue to commit himself to it for the remainder of his term.
“Every day I meet people who strive to make the country better, be it in politics or in civil society, professional or volunteer,” he said.
“To all those who have pushed for me to run again I have been very touched by the arguments, which have brought me much joy.”
A report in Bild on Saturday suggested the President's partner Daniela Schadt had told him he should not run because of the state of his health.
Recent polling suggest that the majority of Germans wanted Gauck to stand for a second term.
Hunt for successor
Parliament would elect Gauck's successor in February 2017.
Conservatives have mooted Finance Minister Wolfgang Schäuble, parliamentary speaker Norbert Lammert, and Bavarian MP Gerda Hasselfeldt, who would be Germany's first female president, as possible candidates.
Berlin's Tagesspiegel newspaper said the horsetrading that is expected in backing a candidate for president was "sure to send a signal" about likely coalitions after the general election.
It said that if Merkel's Christian Democrats had to seek the backing of the opposition Greens to win a majority for their pick, it could lay a foundation for an unprecedented coalition between the parties at the national level.
Merkel, who has been in power since 2006, has not yet announced whether she herself will stand for a fourth term.
She is currently in a left-right grand coalition with the Social Democrats (SPD) but their plummeting support and the desire for more dynamic alliances could push Merkel's conservatives toward the ecologist Greens.
"If Merkel now wants to prevent an SPD candidate, then she will have to find someone who also appeals to the Greens," the right-leaning broadsheet Frankfurter Allgemeine Zeitung wrote.
"That should be manageable."
Such a scenario would also block the potential development of a left-wing alliance between the SPD, the Greens and the hard-left Linke party.
The choice of Hasselfeldt, meanwhile, could help heal a rift between the Christian Democrats and their Bavarian sister party, the Christian Social Union, which has been sniping at Merkel's refugee policy for several months.
The dispute has prompted speculation it could field its own candidate for chancellor rather than backing Merkel.