Billionaire Bill Ackman Has 10.5% of His $19.5 Billion Portfolio in Amazon. What's the Thesis Behind Pershing Square's Bet?

Pershing Square (NYSE: PS), the company headed by high-profile investor Bill Ackman, has emerged as one of the largest corporate bulls on Amazon (NASDAQ: AMZN). Despite recently trimming its stake in the monster retailer as part of a portfolio reallocation, Pershing still holds nearly 8.6 million shares of the company.

According to Pershing's latest 13F filing detailing its equity portfolio, it held more than 8.56 million shares of Amazon as of the end of June. In dollar terms, this amounted to over $2 billion, and 10.5% of that portfolio. Since both numbers are considerable, it's worth looking into Ackman's rationale for being long on Amazon.

The big build-out

Two factors that set Pershing apart from other investment managers are its extreme selectivity in the stocks it holds and its eloquent executive, Ackman, who can rationalize these choices. In the company's second-quarter letter to shareholders, attributed, as usual, to Pershing's founder and CEO, he provided the rationale for continuing to hold Amazon.

He believes investors are generally concerned about the massive amounts of capital being spent on artificial intelligence (AI) infrastructure. That especially applies to Amazon, as the company has indicated it'll ramp up annual capital expenditures (capex) to roughly $220 billion this year, well up from the almost $132 billion of 2025. Much of this spending will be directed to data center build-outs.

This is being done to support the motor of Amazon's growth engine, its powerful and prominent cloud business, Amazon Web Services (AWS). Ackman wrote that AWS has benefited enormously from the broad adoption of AI worldwide, to the point where the segment's revenue has been growing notably -- from 20% in both 2024 and 2025 to over 30% so far in 2026.

And that's just one part of a whole. The retail operations it's better known for are also getting stronger, grabbing market share as it pumps out 15% unit volume growth in the first quarter. This figure, by the way, is the highest growth rate the company has seen since 2021.

Sustainable growth

Gazing into his crystal ball, Ackman added that he and his team believe Amazon can compound total earnings at a pace of at least 20%, which at first glance seems awfully high for a company so huge and well established.

Yet we're living in the age of AI, and many experts believe we're only at the start of a very long and durable growth cycle. Even if the famous investor's view turns out to be somewhat rosy, AWS will still benefit from the uptake, particularly if it's devoting mountains of capital to bolster this business. Meanwhile, that retail arm's poised to continue doing extremely well, too.

I think Ackman is right about Amazon.

Eric Volkman has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Amazon. The Motley Fool has a disclosure policy.