Which mission was the first to use a sky crane to land a rover on Mars?

Mars Science Laboratory was the first mission to use a sky crane to land a rover on Mars.

NASA’s Mars Science Laboratory mission delivered the Curiosity rover to Gale Crater on 6 August 2012. Because Curiosity was too heavy for the airbags used by earlier missions, engineers created a rocket-powered descent stage that hovered above the surface and lowered the rover on cables.

This maneuver, called the sky-crane landing system, allowed Curiosity to touch down on its wheels while the descent stage flew away and crashed at a safe distance. The method reduced the need for Curiosity to carry landing engines and made it possible to place a large scientific laboratory directly on the Martian surface.

Mars 2020 later adapted the same basic approach for Perseverance. Mars Pathfinder used airbags in 1997, so it was not the first sky-crane mission.