克马德克海沟（Kermadec Trench）是地球全深的海沟之一，位于太平洋南部克马德克群岛以东，因太平洋板块沉入印度-澳洲板块形成，海沟长度约1,200公里，最大深度10,047米，与汤加海沟相接。

The Kermadec Trench is one of Earth's deepest oceanic trenches, reaching a depth of 10,047 metres (32,963 ft). Formed by the subduction of the Pacific Plate under the Indo-Australian Plate, it runs over a thousand kilometres parallel with and to the east of the Kermadec Ridge and island arc, from near the northeastern tip of New Zealand's North Island to the trench's junction with the Louisville seamount chain northeast of Monowai Seamount. The Tonga Trench marks the continuation of subduction beyond this point. Subduction south of the Kermadec Trench is marked by the shallower Hikurangi Trench.