LOS ANGELES — It was a storybook marriage in 1986 on a spring weekend on Massachusetts' Cape Cod that united a princess of an American political dynasty, Maria Shriver, and the gap-toothed muscle-bound movie star famous enough to be known by one name, Arnold.
In many ways, it was a pairing of opposites: Her uncle was a U.S. president; his father was an Austrian policeman. She was the rising star of a network-TV news show; he was the pot-puffing star of "Pumping Iron." He was a Republican with a soft spot for Richard Nixon; her family was a pillar in the nation's Democratic establishment.
Former California Gov. Arnold Schwarzenegger and Ms. Shriver announced their separation late Monday, cleaving a sometimes-turbulent 25-year relationship after "a time of great personal and professional transition for each of us," the couple said in a joint statement.
The breakup comes about four months after Mr. Schwarzenegger ended a bumpy, two-term run as California governor, a job his wife never wanted him to pursue. Since then, Mr. Schwarzenegger, 63, has been fashioning a role as an international advocate for green energy, giving speeches and lining up work in Hollywood. Ms. Shriver, 55, has guest-edited an edition of Oprah Winfrey's magazine, but also talked about the stress of changing roles after serving as California's first lady.
The joint statement said the two were working on the future of their relationship while living apart and that they would continue to parent their four children - Katherine, 21; Christina, 19; Patrick, 17; and Christopher, 13.
"After a great deal of thought, reflection, discussion and prayer, we came to this decision together," the statement said.
Ms. Shriver moved out of the couple's gated estate in the Los Angeles neighborhood of Brentwood, but they remain on speaking terms. They had brunch with their children on Mother's Day in a tony restaurant in Santa Monica, Calif., and met privately on their wedding anniversary last month.
Prior to the announcement, there were hints of a rift. The former governor tweeted frequently during his recent travels to Brazil, Nigeria and France, but Ms. Shriver was not mentioned in his online updates from the road. Ms. Shriver, also active on social networks, posted three updates on her Twitter page on the day of their 25th wedding anniversary, April 26, but did not mention the milestone.
About a month before the anniversary, Ms. Shriver wrote on her Facebook page that she was going through a transition in her life.
"As you know, transitions are not easy. I'd love to get your advice on how you've handled transitions in your own life," she said in a video posted on YouTube.
"It's so stressful to not know what you're doing next. People ask you what are you doing, and then they can't believe that you don't know what you're doing," she said.
Mr. Schwarzenegger has often said that Ms. Shriver, who is keenly attuned to the risks of a life in politics, initially was very upset about his plan to run for governor. But when Mr. Schwarzenegger announced his decision on "The Tonight Show With Jay Leno" in August 2003, he said his wife stood by his decision.
During Mr. Schwarzenegger's time in office, Ms. Shriver and the couple's children never moved to Sacramento, Calif., preferring their secluded estate a few miles from the Pacific Ocean. Mr. Schwarzenegger never settled in Sacramento, choosing instead to commute by private jet between his home and the state Capitol.
Ms. Shriver, the daughter of the now-deceased Eunice Kennedy Shriver, left her job as an NBC News correspondent after Mr. Schwarzenegger took office.
In a May 2009 commencement speech at the University of Southern California, Mr. Schwarzenegger alluded to the powerful influence Ms. Shriver had on his life. He said when people ask him the secret to success, "I say, No. 1, come to America. No. 2, work your butt off. And No. 3, marry a Kennedy."
As the state's first lady, Ms. Shriver ran an annual women's conference that attracted a long list of business, political and entertainment luminaries, along with an audience of thousands. She also was credited with overhauling the California Museum in downtown Sacramento, and, with Mr. Schwarzenegger, starting the California Hall of Fame.
In 2007, Ms. Shriver said she wouldn't resume a TV news career after the media circus surrounding Anna Nicole Smith's accidental drug overdose.
"It was then that I knew that the TV news business had changed, and so had I," she said at the time. In a 2009 interview with the Associated Press, she said, "I'm too much of a free spirit" to consider running for elective office.
Ms. Shriver stood by her husband during his campaign after the Los Angeles Times reported accusations that he had a history of groping women. Mr. Schwarzenegger later said he "behaved badly sometimes."
The breakup comes months after the death of Ms. Shriver's father, Peace Corps founder and former vice presidential candidate Sargent Shriver, in January.
• Associated Press writer Daisy Nguyen contributed to this report.