Data center landlord Equinix Inc. is forming a joint venture valued at more than $1 billion with Singapore sovereign-wealth fund GIC Pte. Ltd. to develop and operate data centers in Europe catering to large tenants including major cloud computing operators.

The venture will initially focus on six centers in London, Paris, Frankfurt and Amsterdam. It will develop four of them and buy two existing facilities from Equinix, a Redwood City, Calif.-based real-estate investment trust.

GIC,...