In which ocean would you find the Mariana Trench?

The Mariana Trench is found in the Pacific Ocean.

Located in the western Pacific, the trench lies about 200 kilometres east of the Mariana Islands. It is the deepest known oceanic trench on Earth, with its deepest point, Challenger Deep, reaching approximately 10,984 metres below sea level.

The trench formed at a subduction zone where the Pacific Plate is forced beneath the smaller Mariana Plate. The Pacific Plate's old, cold, and dense oceanic crust sinks into Earth's mantle, creating the exceptionally deep trough. The same tectonic system also helps produce the volcanic Mariana Islands.

Challenger Deep is deeper than Mount Everest is tall, although the comparison is between ocean depth and mountain elevation. The trench is sometimes confused with the Mariana Trough, a nearby back-arc basin; they are related features but are not the same landform.