Uber said Wednesday it made its billionth trip in a new milestone for the global ridesharing service.

"Marvin and Ara just made our day. Their �5 London uberX ride together on Christmas Eve from London Fields, Hackney to Hoxton in Ara's blue Honda Insight Hybrid was the billionth Uber trip," Uber said in a blog posting.

"One billion. That's a whole lot of riders and drivers sharing the road, special moments, and celebrations together. Certainly far more than we ever imagined when we got started in San Francisco five and a half years ago."

Uber has expanded to hundreds of cities around the world in at least 68 countries, offering new options for both riders and drivers but also running into complaints from the taxi industry and regulators.

The company has reached a valuation of more than $50 billion based on private investment disclosed to date.

The billionth ride comes a day after an announcement that fellow San Francisco ridesharing group Sidecar was ending its service.

Uber still faces competition from US-based Lyft and other global startups.

"This holiday season, we're feeling grateful and festive crossing this milestone as we close out the year," the company said.

"For riding their way into our history books, we're putting one year's worth of free rides in rider Marvin's stocking and our driver-partner Ara will be taking a vacation on us to the Uber city of his choice."

Uber said it was also making a donation to Hackney Pirates, a charity serving the neighborhood where the billionth trip started.