Now, after nearly six years of marriage, Holmes is divorcing Cruise. She filed the papers on Thursday, said Cruise's lawyer Bert Fields. The two share a daughter, 6-year-old Suri, who's been featured in celebrity media nearly as frequently as her parents.
But it's telling that even in addressing their split in the typically vague fashion of famous people, Cruise still refers to Holmes by the name he called her: Kate, as if to distance her from the adorable Katie audiences came to know and love from the teen soap "Dawson's Creek."
"Kate has filed for divorce and Tom is deeply saddened and is concentrating on his three children," Cruise's representative, Amanda Lundberg, told The Associated Press. "Please allow them their privacy to work this out."
Holmes' attorney, Jonathan Wolfe, made a similar plea Friday: "This is a personal and private matter for Katie and her family. Katie's primary concern remains, as it always has been, her daughter's best interest."
But we've never been able to leave them alone - and even if we tried, they probably wouldn't let us.
Theirs was a bond that never really made sense on paper, despite Cruise's famously euphoric couch-jumping on "The Oprah Winfrey" show and Holmes' starry-eyed confession that she'd had a crush on the "Top Gun" star when she was a girl. Cruise turns 50 on Tuesday, Holmes is 33.
They'd kiss passionately for the benefit of photographers on red carpets and were all-too happy to share the romantic details of their engagement: He popped the question at the Eiffel Tower in Paris early one morning in June 2005. The wedding itself in November 2006 was a fairy-tale, A-list extravaganza at a 15th century Italian castle before a Church of Scientology minister.
So why didn't we believe them? Maybe because it always felt like they were trying so hard to prove to the world they were in love.
"I can't be cool. I can't be laid-back," Cruise said during his notorious "Oprah" appearance. "Something happened and I want to celebrate it."
Cruise has two children with his previous wife, Nicole Kidman. The actor was also previously married to Mimi Rogers. This was Holmes' first marriage.
Cruise showed up alone at recent premieres of the musical film "Rock of Ages," in which he's earning strong reviews for his performance as an Axl Rose-style lead singer. Holmes also was absent earlier this month when Cruise received the fourth-ever Friars Club Entertainment Icon Award. He said at the time that Holmes was overseas and the family would reunite in Iceland for Father's Day.
Yet a year ago, in receiving an award from Women in Film, Holmes thanked Cruise in the audience, saying his "commitment to his work and family inspires me daily."
Before the relationship, Holmes had drawn acclaim for her work in films like "Wonder Boys" and "Pieces of April." And Cruise was ... well, he was Cruise, one of the biggest stars on the planet. But the marriage, and the general speculation about its legitimacy, seemed to hurt both their images.
It was around the time of the "Oprah" appearance that Sumner Redstone and Paramount broke ties with Cruise after their long relationship. Cruise's company, Cruise/Wagner Productions, then signed a deal with First & Goal LLC.
Redstone was recently quoted by The Hollywood Reporter as saying that he "actually fired Tom. His behavior was terrible ... He was jumping on the couch on the Oprah show. Women hated him. A lot of people said they would never come back and see Tom Cruise."
Kelly Lynch, editor of the pop-culture website Socialite Life, noted Friday the August 2005 W Magazine cover story on Holmes in which a woman described as Holmes' "Scientology chaperone" sat in on the interview and chimed in on her responses, even though Holmes herself was consistently ebullient about Cruise.
The chaperone also deflected particularly pointed or uncomfortable questions about rumors that this love might not be real.
"She wasn't Joey from 'Dawson's Creek' anymore," Lynch said. "It was almost like the life had been sucked out of her when she started dating him."
Her first film back, the 2008 heist comedy "Mad Money," was a critical and commercial failure. That same year, Cruise came out as the eyepatch-wearing star of the Nazi thriller "Valkyrie," which drew mixed reviews but still made $200 million worldwide.
Holmes' recent films include Adam Sandler's "Jack and Jill" and the Emmy-winning mini-series "The Kennedys," in which she played Jackie Kennedy. Cruise, meanwhile, starred in the fourth film in the "Mission: Impossible" series, "Mission: Impossible - Ghost Protocol," which has made more than $690 million worldwide.
Lynch said she was surprised by the demise of the duo dubbed "TomKat" because she figured that, no matter what, Cruise and Holmes would always try to maintain the meticulously crafted image that they were the perfect couple.
"Despite some of my reservations about the relationship, I thought they were happy to kind of swim along as man and wife, despite reports in every sort of magazine that they weren't getting along, that Katie is trapped in the marriage," Lynch said. "But I never truly believed that they were truly in love. It felt very arranged."
How the divorce impacts either of their images or careers remains to be seen, said veteran celebrity publicist Howard Bragman.
"They're both going to be defined by their choices. Tom was never really defined by the marriage. Tom was defined by Tom. He's such a force of nature," he said. "A single Tom Cruise is an interesting phenomenon. I think we'll be hearing about him dating.
"Katie will be fine. I think this raises her to a new level. I think she'll get more active in her career," Bragman added. "She's got talent, beauty, a good family, a good support system, good Midwestern values - these things are all going to serve her. I think mostly she's a good mother. That's what I respect her most for."
AP Entertainment Writer Jake Coyle contributed to this report from New York.