Bill Ackman’s Pershing Square has made Microsoft ( MSFT ) a core holding, with the legendary activist investor arguing the software giant’s roughly 27% economic interest in OpenAI is worth around $200 billion and not reflected in the share price.

Ackman disclosed the new position in a post on X early Friday, ahead of Pershing Square’s 13F filing later in the day.

He said the firm began building the stake in February after Microsoft’s fiscal Q2 results sent shares lower.

Pershing Square USA, Ackman’s newly launched publicly traded vehicle, has also made Microsoft ( MSFT ) a core holding.

The Valuation Case

Pershing established its position at 21 times forward earnings, broadly in line with the market multiple and well below where Microsoft ( MSFT ) has traded over the past few years, according to Ackman.

Microsoft ( MSFT ) shares are down 12% year-to-date and have lost more than a quarter of their value since peaking last fall.

Ackman compared the trade to Pershing’s earlier buys of Alphabet , Amazon ( AMZN ) and Meta Platforms ( META ) , each picked up after sharp drawdowns tied to AI capex anxiety.

The $200 Billion Question

Microsoft’s headline multiple does not reflect its OpenAI stake, which Ackman marked at approximately $200 billion based on the AI lab’s most recent funding round.

That figure represents roughly 7% of Microsoft’s market capitalization. The catalyst that would force Wall Street to mark the stake is an IPO, and prediction market traders are not betting on one any time soon.

Polymarket gives OpenAI just a 26% chance of listing by Dec. 31. Anthropic, OpenAI’s main competitor, is priced at 68% to IPO before OpenAI.

Polymarket also gives OpenAI just a 7% chance of holding the top AI model by the end of June, behind Anthropic and Google ( GOOG ).

The M365 Pricing Reset

Ackman said investors underestimate the resilience of the productivity suite, which is used by over 450 million workers daily and generates average revenue per user of around $20.

Recent investor jitters have centered on competitive threats from AI lab offerings, including Anthropic’s Claude Cowork.

The hedge fund manager pointed to Microsoft’s shift from pure per-seat licensing to a hybrid model of seats plus metered consumption, which lets the company capture incremental revenue as AI agents drive usage that a flat seat structure would leave on the table.

He added that CEO Satya Nadella is directly involved in prioritizing Copilot’s rollout, and that the business unit grew 15% in constant currency last quarter.

Azure, Microsoft’s cloud platform and the world’s second-largest hyperscaler, grew 39% in constant currency last quarter, with guidance for modest acceleration.

The company has lifted its calendar 2026 capex budget to roughly $190 billion, two-thirds of it on servers and networking gear that drives near-term revenue.

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