What is the name of the canyon system on Mars over 4,000 km long?

The canyon system on Mars over 4,000 km long is Valles Marineris. It runs mostly east–west near Mars's equator, east of the Tharsis volcanic region, and stretches for nearly a quarter of the planet's circumference.

Valles Marineris is more than 4,000 km long, up to about 200 km wide, and reaches roughly 7 km in depth, making it the largest known canyon system in the Solar System. It is not a single narrow gorge like Earth's Grand Canyon, but a connected network of enormous chasmata and valleys.

The system was named after NASA's Mariner 9 orbiter, which discovered it while mapping Mars in 1971–72. Its western end begins near Noctis Labyrinthus, while its eastern channels eventually lead toward the Chryse Planitia region.

A common mix-up is Mariner Valley, a loose English translation of the Latin name. Olympus Mons is instead a giant volcano, and the Grand Canyon is located on Earth.