OpenAI has closed a new $40 billion financing round that values the artificial intelligence company at $300 billion, according to people familiar with the transaction cited by Reuters. The deal marks one of the largest private fundraising rounds ever completed by a technology company.

Microsoft is said to have provided the largest share of the capital. The company has already been one of OpenAI’s most important commercial and strategic partners, and the latest investment deepens that relationship as demand for generative AI tools continues to surge.

The new valuation underscores how aggressively investors are still betting on AI infrastructure and software, despite rising concerns about competition, regulation, and the cost of building advanced models. For OpenAI, the funding offers fresh capital to expand products, compute access, and enterprise offerings.

The transaction also reflects the broader race among major technology firms to secure an early lead in artificial intelligence. As rivals pour money into model development and cloud capacity, OpenAI’s latest raise places it among the most closely watched and heavily funded companies in the sector.