The deal, at roughly double the valuation OpenAI fetched as recently as February, underscores investors’ red-hot expectations for the generative AI boom that OpenAI ignited with its 2022 release of ChatGPT.

“The new funding will allow us to double down on our leadership in frontier AI research, increase compute capacity, and continue building tools that help people solve hard problems,” OpenAI said in its announcement of the deal on Wednesday.

The funding comes as the nine-year-old AI startup led by CEO Sam Altman faces increasing competition from the likes of Google, Meta, and other AI startups, and at a time when OpenAI is dealing with its own growing pains—most famously, a boardroom coup last year in which Altman was briefly fired and then reinstated in a span of five days.

Since then, the company has been roiled by a string of high-level departures as it seeks to evolve from its roots as a nonprofit research lab to a producer of commercial products capitalizing on the industrywide AI gold rush. Last month, OpenAI chief technology officer Mira Murati unexpectedly resigned to “create the time and space to do my own exploration.” And as Fortune reported this week, some insiders have voiced concerns that the company’s commitment to safety has taken a back seat in the rush to release new products ahead of rivals.

Despite the internal turmoil, investors appeared eager to get a piece of the startup.

OpenAI did not disclose the names of the investors, but venture capital firm Thrive Capital confirmed to Fortune in an email that it had invested and led this latest round. According to Bloomberg, which first reported news of the deal, Khosla Ventures, Altimeter Capital, Fidelity, SoftBank, and Abu Dhabi–based MGX also participated in the round, along with AI chipmaker Nvidia and Microsoft, which has previously invested $13 billion in OpenAI. While Apple was reported to have been exploring the possibility of investing in OpenAI, the iPhone maker is not involved in the round, Axios reported, citing a source.

250 million weekly ChatGPT users

With the funding, OpenAI cements its status as one of the most valuable startups in the world, trailing TikTok owner ByteDance, valued at $225 billion, and Elon Musk’s $200 billion space exploration company SpaceX, according to CB Insights’ list of unicorn tech company valuations.

OpenAI said Wednesday that more than 250 million people around the world use ChatGPT every week. The company does not disclose its financial results, though the New York Times reported that OpenAI’s monthly revenue reached $300 million in August and that it projects generating $11.6 billion in revenue next year.

With OpenAI’s new $157 billion post-money valuation, investors appear to be valuing the company at 13 times its projected revenue next year. By contrast, Google parent company Alphabet trades on the public market at 5.3 times its projected revenue next year, while Nvidia trades at roughly 16 times projected revenue.

OpenAI referred to its founding principles on Wednesday, stating that it was “making progress on our mission to ensure that artificial general intelligence benefits all of humanity.” Artificial general intelligence, or AGI, is the still-theoretical notion of an AI system that can handle tasks as well as or better than humans are able to. The potential dangers of AGI were part of the reason OpenAI was founded in 2015, as Altman, Elon Musk, and the other cofounders sought to create a counterweight to Google’s DeepMind, which, they feared, would develop AGI based on purely commercial interests.

Musk, who later left OpenAI, has accused the firm of abandoning its original mission, even as he has launched his own commercial AI business, xAI.

OpenAI’s valuation has nearly doubled from its level earlier this year, when it conducted a tender offer for employees to sell some of their shares to private investors in a deal that valued the company at around $80 billion.