Kishida was elected president of his governing Liberal Democratic Party in 2021 and his three-year term expires in September.
His drop out of the race means a new leader who wins the party vote will succeed him as prime minister because the LDP controls both houses of parliament.
Kishida, stung by his party’s corruption scandals, has suffered dwindling support ratings that have dipped below 20%.
Kishida was set to explain his decision in a press conference later Monday.
Local election losses earlier in the year eroded his clout, and LDP lawmakers have voiced the need for a fresh face ahead of the next general election.
Since the corruption scandal broke, Kishida has removed a number of Cabinet ministers and others from party executive posts, dissolved party factions that were criticized as the source of money-for-favor politics, and passed a law tightening political funds control law. But support for his government has dwindled.
The scandal centers on unreported political funds raised through tickets sold for party events. It involved more than 80 LDP lawmakers, mostly belonging to a major party faction previously led by assassinated former Prime Minister Shinzo Abe. Ten people – lawmakers and their aides – were indicted in January.