The Mariana Trench (or Marianas Trench) is the deepest part of the world's oceans, and the deepest location on the surface of the Earth's crust. It has a maximum depth of about 11 km (6.8 mi), and is located in the western North Pacific Ocean, to the east and south of the Mariana Islands, near Guam.

The trench forms the boundary between two tectonic plates, where the Pacific Plate is subducted beneath the Philippine Plate. The bottom of the trench is farther below sea level than Mount Everest is above it (8,848m/29,028ft). At the bottom, the water column above exerts a pressure of 108.6 MPa, over one thousand times the standard atmospheric pressure at sea level.