Newsom is a Democrat who took office in January and a long-standing opponent of the death penalty, which was last carried out in California in 2006.
"The death penalty is inconsistent with our bedrock values and strikes at the very heart of what it means to be a Californian," Newsom will say, according to prepared remarks from his office.
"The intentional killing of another person is wrong. And as governor, I will not oversee the execution of any individual," he will say.
The governor plans to sign an executive order to block the death penalty in his state. It will also withdraw California's lethal injection protocol and close the execution chamber at San Quentin prison, his office said.
It does not provide for the release of any death row inmates from prison.
A quarter of all those on death row in the United States are in California, according to the governor's office. Twenty-five people on California's death row have exhausted all of their appeals.
President Donald Trump said Newsom was "defying voters" in halting the death penalty for "stone cold killers."
"Friends and families of the always forgotten VICTIMS are not thrilled, and neither am I!" he added on Twitter.
Senator Kamala Harris, who is among a crowded field of candidates seeking the Democratic presidential nomination, said she welcomed Newsom's move to end the "deeply flawed system of capital punishment in California."
"The death penalty is immoral, discriminatory, ineffective, and proven to be unequally applied," she added.
Human Rights Watch said that with the governor's decision, California continues a trend in the United States away from putting people to death.
The state joins Colorado, Oregon, and Pennsylvania, which have similar bans, and 20 states that have abolished the death penalty, it said.
"Governor Newsom has demonstrated great courage and leadership in ending the cruel, costly, and unfair practice of executing prisoners," said Alison Parker, US managing director at Human Rights Watch.
"Californians should be proud their state has taken a stand to end state-sanctioned killing and uphold the human rights of all people."
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