Which company operated the Ariane flight that launched JWST?

Arianespace operated the Ariane flight that launched the James Webb Space Telescope.

The mission was designated Ariane flight VA256 and used an Ariane 5 ECA+ rocket. It lifted off on 25 December 2021 from the Guiana Space Centre in French Guiana, carrying Webb toward its journey to the Sun–Earth L2 point. Arianespace was the launch-service provider and mission operator, while ArianeGroup manufactured the Ariane 5 launcher.

This distinction is easy to miss because several major aerospace companies were associated with Webb. NASA led the mission with ESA and the Canadian Space Agency; Northrop Grumman built much of the spacecraft and sunshield, while Ariane 5 provided the launch. United Launch Alliance, Blue Origin and SpaceX did not operate this flight.

VA256 was especially important for Ariane 5 because Webb was an exceptionally large, valuable and delicate payload. The launch was successful, and the telescope separated from the rocket after reaching its initial trajectory. Webb later used its own propulsion system for course corrections before entering its halo orbit around L2.