Microsoft has disclosed that its stake in OpenAI is valued at $135 billion, which is roughly equivalent to about a quarter of the new OpenAI Group PBC. This figure appeared in documents related to an employee stock sale scheduled for October 2025. The information is particularly significant because regulators and lawmakers now view both companies as a single entity in legal and regulatory terms.
The $135 billion valuation is part of a broader reorganization that has raised OpenAI’s total value to $500 billion, a significant increase from previous valuations of $300 billion and $157 billion. This restructuring has given rise to a new public-benefit company that could share code with competitors and release open-weight models. In return, Microsoft retains priority over new models and products through the end of 2032.
Since 2019, Microsoft has invested roughly $13.75 billion in OpenAI. The initial agreement stipulated that up to 75% of OpenAI’s revenues would go back to Microsoft until it recouped its investment, after which it would be set at 49%. Accounting records already show charges of $3.1 billion and $4.7 billion related to this alliance.
Revaluation and restructuring of OpenAI
The relationship between the two companies faces challenges beyond the financial. Antitrust investigations are underway in several countries, while various class-action lawsuits — including one filed by a cofounder — allege that the duo has strayed from OpenAI’s original mission and violated competition rules. Internally, OpenAI has considered filing an antitrust complaint against Microsoft over its control of hosting on Azure.
For markets and corporate treasuries, the risk is clear: if a single cloud provider controls the models, any disruption, ban, or price increase could paralyze tokenized services or platforms that integrate AI into everyday workflows. For investors, regulatory intervention or the loss of exclusivity would force a rapid revaluation of any company with exposure to AI.
The next critical moment will be determining whether the contracts scheduled through 2030 hold or break under legal pressure, a decision that will signal to the market whether the duo remains a united team or becomes two separate rivals in a fragmented AI field.
