AirAsia X has ordered 10 Airbus A350-900 aircraft and placed options on five more.
The Malaysian low-cost long-haul carrier disclosed the agreement at the Paris Air Show today.
First deliveries of the aircraft are due to take place in the first quarter of 2016.
AirAsia X had been weighing up the A350 against the Boeing 787 but earlier this month indicated it had settled on the Airbus twin-jet.
A350s are currently available only with the Rolls-Royce Trent XWB engine.