Oceanic Trenches are the long narrow topographic depression in the ocean floor. Ocean trenches mark the position at which the sub ducting slab begins to descend beneath another lithospheric slab.
Some of the important trenches in the major oceans of world are given below:
| Trench name | Ocean | Depth (m) |
| Mariana Trench | Pacific Ocean | 11033 (36,198ft) |
| Tonga Trench | Pacific ocean | 10882 (35,702ft) |
| Philippine trench | Pacific ocean | 10540 (34,580ft) |
| Puerto Rico trench | Atlantic Ocean | 8800 (28,900ft) |
| Java trench/ Sunda Trench | Indian Ocean | 7725 (25344ft) |
| Litke Deep (Eurasian Basin) | Arctic ocean | 5449 (17881ft) |