The James Webb Space Telescope was launched on an Ariane 5 rocket. The launch vehicle and launch site were part of the European Space Agency's contribution to the mission. The Ariane 5 is one of the world's most reliable launch vehicles and was chosen for a combination of reliability (it was the only launch vehicle that met NASA's requirements for launching a mission like Webb) and for the value it brought via our international partnership. Read more about why the Ariane 5 was chosen.