The company, which is marking its 20th year in business, retails a variety of luxury new, used and vintage watches, as well as accessories.
It made the announcement on Instagram on Wednesday with a picture of the football player and the digital platform's co-chief executive and founder Tim Stracke.
“As an athlete it takes him roughly 90 minutes to win. As an obsessive watch collector, he did it in seconds. Watch lovers all over the world, we have amazing news for you: Cristiano Ronaldo, the football unicorn just joined Chrono24 as shareholder,” the online marketplace said.
“His passion for timepieces met his business genius and he’s taking both to the next level. It’s a big day for us and our community, whose love for watches knows no bounds. A victory for the art itself. And a proof that dreams can be achieved with feet, brains and infinite devotion.”
The value of the investment was not disclosed.
Previous Chrono24 investors include Bernard Arnault’s family investment company, Aglae Ventures, General Atlantic, Insight Partners and Sprints Capital – who together led Chrono24’s series C round in August 2021, worth $118 million, which valued the marketplace at more than $1 billion.
Other investors in Chrono24 include Sprints Capital, former Richemont director Gianni Serazzi and Yoox-Net-a-Porter founder Alberto Grignolo.
Chrono24 has more than 530,000 watches from 3,000-plus dealers and 30,000 private sellers across 120 countries. The portal reaches more than nine million unique visitors per month.
Ronaldo, 38, who is known by fans as CR7, became the first footballer to cross $1 billion in career earnings in 2020.
He is an avid watch collector. His collection includes a rare $2 million Girard-Perregaux Planetarium Tri-Axial, as well as numerous pieces from Jacob & Co, Rolex, Breguet, Cartier, Franck Muller, Hublot, Van Cleef & Arpels, among others.
“No one brings passion for luxury watches to the world stage quite like Cristiano,” Mr Stracke said.
“He has already solidified his place as one of the greatest athletes in history and, as an investor, shows astute knowledge of world-class luxury and technology.
“That, coupled with his authentic, proven passion for watch-collecting, makes him the perfect teammate as our company moves further into global expansion and our next chapter.”
The football star's lifetime earnings are estimated at about $1.24 billion, after reaping in $136 million last year, according to Forbes. He has a net worth of $500 million after tax, according to wealth tracking website Celebrity Net Worth.
“As a long-term watch collector and regular user of Chrono24, it’s a pleasure for me to become a shareholder in the company now,” Ronaldo said.
“Chrono24 unites millions of watch lovers from all around the world to share in their passion, together – that global unification is something I know well and am thrilled to be a part of.”
He has a lifetime deal with Nike and earns money off the pitch through his CR7-brands.
The five time Ballon d’Or winner is an investor in CR7 Hotels, a joint venture he struck with Pestana Hotel Group, a Portuguese company that was rebranded Pestana CR7.
The athlete who has more than 850 million social media followers, also owns the CR7 Denim brand, as well as other clothing lines. He also has a collaboration with perfume company Eden Parfums that sells his CR7 Fragrances line.
Ronaldo has also teamed up with Mabel Hospitality, the arm of Mabel Capital, a private investment firm owned by business partners Manuel Campos Guallar, Abel Matutes Prats and tennis star Rafael Nadal.
The company focuses on the development of restaurant brands such as Tatel and Toto, with locations in Abu Dhabi, Bahrain, Beverly Hills, Doha, Ibiza, Madrid, Riyadh, Mexico City and Valencia.
Other investments by the athlete include CR7 Crunch Fitness, a franchise of fitness centres.