An intruder who broke into the home of Nancy Pelosi and her husband was searching for the US House Speaker, police say.
The attacker broke into the couple's San Francisco home via the back door at around 2.30am on Friday, armed with a hammer.
Police chief William Scott said officers were called to the house for a "wellbeing check" and arrived to find both men holding the hammer.
The suspect then pulled the hammer away from Paul Pelosi and used it to "violently assault" him, before being tackled by police officers.
At some point, the suspect had shouted "Where is Nancy? Where is Nancy?", NBC News reports.
David Depape, 42, was named by police as the suspect.
He will be charged with attempted homicide, assault with a deadly weapon, elder abuse, and "several other additional felonies", the police chief said.
Mr Pelosi, who owns a San Francisco-based real estate and venture capital firm, was taken to hospital, where he is "expected to make a full recovery", spokesman Drew Hammill said.
A Pelosi family member said Mr Pelosi was still in surgery after being hit in the head with a hammer multiple times, while Mrs Pelosi is on her way to San Francisco to be with him.
The family member said Mr Pelosi had been home alone when the intruder entered and that the intruder had wanted to tie him up "until Nancy got home".
When the police came, the suspect had said: "We are waiting for Nancy," the family member said.
Mrs Pelosi, the Democratic speaker of the US House of Representatives, and second-in-line to the presidency, was in Washington DC at the time, having recently returned from a security summit in Europe.
Had she been at home, her security detail would have been present but Mr Pelosi is not eligible for this protection on his own.
Senate Majority Leader Chuck Schumer said in a statement: "What happened to Paul Pelosi was a dastardly act.
"I spoke with Speaker Pelosi earlier this morning and conveyed my deepest concern and heartfelt wishes to her husband and their family, and I wish him a speedy recovery."
'The president is praying'
The White House said in a statement: "The president is praying for Paul Pelosi and for Speaker Pelosi's whole family.
"This morning he called Speaker Pelosi to express his support after this horrible attack.
"He is also very glad that a full recovery is expected."
The attack is being investigated by San Francisco police, Capitol Police and the FBI.
It comes amid growing concern about the safety of America's politicians almost two years after the Capitol insurrection in January 2021, when Mrs Pelosi's office was ransacked.
Last year, Capitol Police investigated around 9,600 threats made against members of Congress from both parties - nearly a threefold increase since 2017.