$24.1 billion. That is what Microsoft (MSFT) generated in AI revenue attributable to OpenAI in the fiscal year ending June, a figure that places one external partner at more than half of the company's total AI business, and possibly as much as 70%. The commercial scale is real. The concentration is a problem worth pricing.
What the figure actually says
"More than half" is one read of the OpenAI relationship. "Potentially as much as 70%" is the more alarming one. At the lower end, Microsoft looks like a company that built early and captured outsized share by going all-in on OpenAI. At the higher end, the dependency is the business.
The case for MSFT is that $24.1 billion in annual AI revenue is revenue already on the books, not a projection or an addressable market estimate. For the buy-side, that distinction matters. Narrative without numbers is a thesis. This is both: a verifiable revenue figure tied to one of the most-discussed technology relationships in the market. Portfolio managers who want AI exposure backed by something other than a promise have found a number to anchor on.
The counterargument deserves its paragraph
Microsoft has been building proprietary AI models and has invested in Anthropic, a direct OpenAI competitor. Those two moves are the official hedge: if the OpenAI relationship deteriorates, or the commercial terms shift, Microsoft will have alternatives in development and a financial stake in a rival. The counterargument is that Microsoft's management sees the concentration risk and is spending against it. The $24.1 billion figure is a feature of the current period, not a permanent state.
The question investors cannot yet answer is pace. Proprietary models and Anthropic exposure are not yet generating a disclosed revenue figure that rivals what OpenAI contributes.
On balance
The arithmetic stays simple. OpenAI produced more than half, and possibly 70%, of Microsoft's AI revenue in the fiscal year ending June. That is the read-through for anyone building a position on Microsoft's AI segment: diversification is the strategy, but OpenAI is still the business. Microsoft's own models and its Anthropic investment have ground to make up. At up to 70%, that gap is not small.