The deepest part of the ocean is called the Challenger Deep and is located beneath the western Pacific Ocean at the southern end of the Mariana Trench, which runs several hundred kilometers southwest of the U.S. territorial island of Guam. Challenger Deep is approximately 35,876 feet deep. It is named after the HMS Challenger, whose crew first sounded the depths of the trench in 1875. In contrast, the average depth of the ocean is about 12,100 feet.

Source: National Ocean Service