Which is the deepest trench in the world not located in the Pacific Ocean?

The deepest trench in the world not located in the Pacific Ocean is the Puerto Rico Trench.

It lies north of Puerto Rico, along a complex boundary involving the Caribbean, North American, and South American plates. The trench extends for roughly 810 kilometres and reaches the deepest known point in the Atlantic Ocean.

Its deepest area is commonly called the Milwaukee Deep, although the nearby seabed is also known as the Brownson Deep. Modern mapping and direct measurements have produced depth figures in the range of about 8,376 to 8,740 metres, depending on the survey method and the exact point measured.

The South Sandwich Trench is a common mix-up: it is also in the Atlantic region and is the deepest trench in the Southern Atlantic, but its maximum depth is about 8,266 metres—roughly 110 metres shallower than the Puerto Rico Trench. The Puerto Rico Trench is therefore the deepest non-Pacific trench.