Billionaire Bill Ackman Is Buying a Brilliant Robotaxi Stock Up 145% in 2 Years (Hint: Not Tesla)

Billionaire Bill Ackman is the CEO of Pershing Square Capital Management, a hedge fund that returned 210% in the past five years. Comparatively, the S&P 500 (SNPINDEX: ^GSPC) advanced 101% during the same period. Those market-beating results make Ackman a good source of inspiration for individual investors.

Since January, Ackman has bought more than 30 million shares in a robotaxi stock that has soared 145% in the past two years. I'm not referring to Tesla, though the company also plans to launch an autonomous ride-sharing service in Austin this year. Instead, the stock Pershing Square has been buying is Uber Technologies (NYSE: UBER).

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Here's what investors should know.

Uber is a leader in the ride-sharing and food-delivery markets

Uber operates the largest ride-sharing service and second-largest restaurant food delivery service in the U.S. as measured by revenue, according to Bloomberg. The company is also the ride-share leader in nine other countries and the food-delivery leader in seven countries.

That scale affords Uber an important competitive advantage. It makes the network effect inherent to its business particularly powerful, such that monthly active users increased 14% and trips increased 19% last year. That means the number of users in not only increasing, but also those users are engaging the platform more frequently.

Scale also supports cost-efficient user acquisition because Uber can market mobility services to delivery app consumers and vice versa. The company is exploiting that opportunity: 31% of first-time delivery trips come from the mobility app, and 22% of first-time mobility trips come from the delivery app.

Finally, the company is deepening its consumer relationships through product innovation and the Uber One membership program. Last year, multiproduct adoption reached a record 37% of consumers, and Uber One members increased 60% to 30 million people.

Uber is ideally positioned to be a winner as robotaxis become more prevalent

Uber's leadership in the ride-sharing market means it can effectively aggregate demand for companies with autonomous vehicle (AV) fleets. CEO Dana Khosrowshahi told analysts on the fourth-quarter earnings call, "Uber is uniquely positioned to offer tremendous value for AV players looking to deploy their technology at scale."

Uber has already partnered with 14 autonomous driving technology companies, including Alphabet's Waymo. That particular partnership dates back to October 2023, when Uber began matching riders with Waymo robotaxis in Phoenix. The partnership expanded in April 2024, when Uber Eats started using Waymos for autonomous food delivery.

In March 2025, the companies collaborated to bring robotaxis to Austin -- that may have been a shot at Tesla given that its corporate headquarters is in Austin. Uber and Waymo also plan to launch robotaxis in Atlanta in the coming months. If those partnerships prove fruitful for both parties, it would underscore what CEO Dana Khosrowshahi has said about Uber being "an indispensable partner for AV players."

Going forward, Uber believes autonomous ride-sharing will be a $1 trillion market in the U.S. alone. So, when accounting for its global scale, Uber has a multitrillion-dollar market opportunity in robotaxis.

Image source: Getty Images.

Uber stock is worth buying at its current price

Uber reported solid financial results in the fourth quarter. Revenue increased 20% to $12 billion on particularly strong sales growth in the mobility segment. Additionally, adjusted EBITDA increased 44% to $1.8 billion as take rate improved across the mobility and delivery segments, meaning the company kept more of each dollar spent on its platform.

Turning to the future, Uber estimates annual adjusted EBITDA growth will range from high-30% to 40% over the next three years. That hints at similar growth in adjusted earnings, which makes the current valuation of 17 times earnings look very reasonable. Investors should feel comfortable buying a small position in this brilliant robotaxi stock today.

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Suzanne Frey, an executive at Alphabet, is a member of The Motley Fool's board of directors. Trevor Jennewine has positions in Tesla. The Motley Fool has positions in and recommends Alphabet, Tesla, and Uber Technologies. The Motley Fool has a disclosure policy.