The setting for their first encounter could hardly have been less romantic -- they happened to have ringside seats close to each other at a World Heavyweight boxing match in Hamburg. With introductions out of the way, they soon struck up an easy conversation. He waxed lyrical about Manchester United; she talked about her love of Liverpool.
In the fight, David Haye took a ferocious beating from Wladimir Klitschko; outside the ring, Rory McIlroy and Caroline Wozniacki were smitten. Within weeks, golf's bright young thing and the world's number one tennis star were an item -- a match made in (sports marketing) heaven.
Having announced a split with childhood sweetheart Holly Sweeney around the time he met Wozniacki, McIlroy wasted little time in pursuing romance. His relationship with the blonde Amazonian Dane has been played out on Twitter and, more recently, through the lenses of the paparazzi.
With David and Victoria Beckham long-established as a celebrity union and Mike Tindall and Zara Phillips's marriage attracting tabloid scrutiny, the coupling of two of the most exciting names in contemporary sport was always going to arouse keen interest.
On Sunday, Caro -- as she likes to be known -- travelled to China to watch her beau scoop the biggest paycheque of his career, a cool $2m (€1.45m) for winning the Shanghai Masters after sinking a pressure putt in a tie-break.
The week before, McIlroy had been by Wozniacki's side in Istanbul in an end-of-season tournament that saw her consolidate her status at the summit of women's tennis.
Next week, the pair will embark on a two-week holiday -- some much needed "we time" away from the globe-trotting demands of pro-sport. As well as catching some sun, they are expected to spend time visiting family and friends. Wozniacki has already been to McIlroy's hometown, Holywood, Co Down, where she met his parents.
Aged just 21 and 22 -- McIlroy is 14 months older -- the couple have each enjoyed an outstanding 2011. McIlroy captured his first Major, the US Open, in July, and Wozniacki displayed her formidable talents as a hard-court specialist on the Women Tennis Association's punishing tour.
Both are hugely ambitious. "I want to become the best player in the world," McIlroy said. "I think we definitely spur each other on. She's number one in the world and I've got a Major and we sort of both want what each other has. She's got a great work ethic and it's something I can probably learn a lot from."
The pair made $20m between on-course and court endeavours and sponsorship deals.
Already, marketers reckon "Wozzilroy" -- to borrow the expression Wozniacki coined on Twitter -- will enjoy a greater pulling power money-wise than the world's most high-profile current couple, Russian tennis ace Maria Sharapova and her Slovenian fiancé, Sasha Vujacic, a basketball player on a $3m-a-year deal in the US.
Their profiles are already lofty -- SportsPro Media, a British sports industry news magazine, rates Wozniacki as the ninth most marketable athlete in the world, with McIlroy at number 21. A long list of blue-chip brands have attached themselves to the pair including, in McIlroy's case, Santander Bank and the luxury hotel chain, Jumeirah, and Wozniacki's, Danske Bank and adidas.
Nigel Currie of UK sports agency Brand Rapport believes Wozzilroy's couple status is likely to make both even more attractive to brands and they could boost their earnings by as much as 50pc as a result of their union, particularly in giant, emerging economies such as China and India. "Suddenly, lifestyle and fashion magazines will be interested in McIlroy because he is Wozniacki's boyfriend, when they would never have shown much interest in a golfer."
Michael Cullen, editor of the Dublin-based Marketing magazine, concurs: "It's early days yet but if they stay together they would likely be very appealing for all sorts of brands. Being a couple can only help their brands to grow."
"Woods was exceptional," Cashmore says. "Not only was he the first black golfer, but he was contracted to Nike. I doubt if any other golfer will occupy the same status, at least not for a decade. I think if McIlroy dominated golf in the same way as Federer used to dominate tennis, or the way Djokovic does now, he would pull in some major endorsements from soft drinks or fast food chains etc. These are the endorsements that help project a celeb from sport into the every day."
But with McIlroy planning to relocate to Florida next year to play the US PGA circuit, his profile is bound to increase yet further, especially if he can add a second Major to his CV. Wozniacki, meanwhile, divides her time between homes in Monte Carlo and Florida.
"He's very much his own man," says golf broadcaster Denis Kirwan, who has known McIlroy since he was a teenage sensation.