What is the deepest ocean trench in the world?

The deepest ocean trench in the world is the Mariana Trench. It lies in the western Pacific Ocean, roughly east of the Mariana Islands, and forms part of a major subduction zone where the Pacific Plate descends beneath the Mariana Plate.

Its deepest section is called Challenger Deep, a small basin at the trench’s southern end. Modern surveys place Challenger Deep at approximately 10,900 to 11,000 metres below sea level—deep enough to submerge Mount Everest with room to spare. Exact measurements vary slightly because sonar readings and depth calculations have margins of uncertainty.

The trench was first sounded during the 1872–1876 HMS Challenger expedition. In 1960, Jacques Piccard and Don Walsh became the first people to reach its floor aboard the bathyscaphe Trieste. Film director James Cameron made a solo descent in 2012 using the Deepsea Challenger.

The Tonga Trench is another exceptionally deep Pacific trench, but it is shallower than the Mariana. The Puerto Rico and Java trenches are also deep, yet neither approaches Challenger Deep.