NVIDIA Helios is a large GPU cluster operated by NVIDIA, in the private sector. It came online around November 2023. At that moment it ranked number 46 among known clusters.
It is built on 1,024 NVIDIA GH200. That amounts to about 1K H100e of AI compute. The cluster draws roughly 1.49 MW. Its hardware is estimated at $47M.
Epoch AI rates the certainty of this record as confirmed. They announced in May 2023 that they were building it and that it would be operational by the end of the year. They haven't publicly confirmed that it is operational, but it seems very likely that it is