Nebius jumped 12% in premarket trading Thursday after Situational Awareness, the hedge fund run by former OpenAI researcher Leopold Aschenbrenner, disclosed a major stake in the AI cloud company.
According to its 13G filed Wednesday, the fund reported owning 12.4 million Class A shares of Nebius, representing a 5.6% stake worth ~$2.6 billion as of Wednesday’s closing price. The position didn’t appear in the fund’s most recent 13F filing — which covered holdings as of March 31 and included other neocloud companies such as CoreWeave and IREN — suggesting the Nebius stake was added sometime after the first quarter.
The disclosure puts Situational Awareness among Nebius’s largest disclosed institutional shareholders, at least based on the latest available ownership filings, which show Blackrock as the largest institutional holder as of March 31, with 4.5% of shares outstanding.
One of the "neocloud" stocks, Nebius has gained traction recently after securing large cloud contracts with Microsoft and Meta, as well as an equity investment from Nvidia and an energy partnership with Bloom. Shares are up **165% **this year and a whopping **475% **over the past 12 months.
Founded in 2024 by Aschenbrenner — and named after his widely-read essay on artificial superintelligence — Situational Awareness has built its portfolio around the physical infrastructure AI runs on, from chips and data centers to power and compute. Per its 13F filings, the fund’s reported portfolio value climbed to $13.7 billion as of the first quarter, up
nearly 2.5x from
$5.5 billionat the end of 2025.