European AI cloud firm Nebius is partnering with UK operator Ark.

Ark Data Centres this week announced that it has signed a long-term agreement with Nebius to host an Nvidia Blackwell Ultra GPU deployment installed at Ark’s Longcross Park campus in Surrey.

Set to go live this year, the Longcross site in Chertsey will total 54MW across two data centers.

The cluster will comprise an initial deployment of 4,000 Blackwell Ultra GPUs, hosted in a purpose-built, liquid-ready data hall at Longcross Park.

Huw Owen, CEO, Ark Data Centres, said: “AI clouds need sites that can deliver high-density cooling today and scale rapidly tomorrow. Longcross Park was engineered precisely for that challenge, and we are delighted to welcome Nebius to the UK as a key AI tenant.”

Nebius announced it was planning to deploy thousands of the Nvidia Blackwell Ultra GPUs – aka B300s – earlier this month, but didn’t reveal where they would be hosted.

The deployment is expected to be operational by Q4 2025. Ark said the site will include on-site power generation.

With the addition of the UK, Nebius will eventually operate seven AI clusters in six countries across Europe, the US, and the Middle East. Three are currently live across Finland, the US, and France.

Andrey Korolenko, chief product and infrastructure officer at Nebius, said: “Partnering with Ark gives us access to an environment built for the next wave of GPU innovation, with the right infrastructure that is needed to support today’s highly intensive AI cloud workloads. By locating compute resources close to the UK’s world-class start-ups, enterprises, researchers, and public-sector innovators, we will enable them to move faster from idea to implementation.”

Nebius was formed last year after Russian tech firm Yandex's European operations were spun off into a separate entity. Based in Amsterdam, Nebius took control of Yandex's Finnish data center, its Nebius AI unit, as well as data firm Toloka AI, edtech provider TripleTen, and autonomous driving firm Avride.

The company is aiming to achieve a baseline of 100MW of capacity in 2025, but according to COO Roman Chernin, the ambition is actually to grow “much larger and much faster,” with the company looking to build a data center pipeline to provide "scalability to more than 1GW of power.”

In the US, the company is working with DataOne to develop a 300MW data center in New Jersey, the first phase of which is expected to go live in the summer of 2025. Nebius is also set to lease space at an upcoming data center in Kansas City, Missouri.

The company has further colocation presence in Iceland and France, the latter in an Equinix facility in Paris.

In May 2025, Nebius revealed it would build and operate a $140 million national supercomputer in Israel, part-funded by the Israeli government's Innovation Authority.

Founded in 2005, Ark has 27 data centers across nine sites in the UK and Belgium in operation or development, totaling more than 560MW. It operates data center campuses at Cody Park in Farnborough, Meridian Park in north London, and Spring Park in Wiltshire's Corsham, with a number of projects in development, including Union Park and Alliance Park in west London.

Controlled by Elliott Investment Management with Revcap as a minority investor, Ark serves a number of UK government departments and agencies, and also has a joint venture with the Cabinet Office called Crown Hosting to provide colocation services to public sector bodies and government departments.