罗曼什海沟（Romanche Trench），亦被称为罗曼什水平沟（Romanche Furrow）、罗曼什裂口（Romanche Gap）、罗曼什断裂带（Romanche Fracture Zone），为大西洋第三深海沟，在波多黎各海沟、南桑德韦奇海沟之后。罗曼什海沟在赤度以北把大西洋洋中脊一分为二，位置在大西洋最狭窄的地方，即巴西与西非之间，在北纬2度至南纬2度与西经16度至西经20度间伸延。

The Romanche Trench, also called the Romanche Furrow or Romanche Gap, is the third deepest of the major trenches of the Atlantic Ocean, after the Puerto Rico Trench and the South Sandwich Trench. It bisects the Mid-Atlantic Ridge (MAR) just north of the equator at the narrowest part of the Atlantic between Brazil and West Africa, extending from 2°N to 2°S and from 16°W to 20°W. The trench has been formed by the actions of the Romanche Fracture Zone, a portion of which is an active transform boundary offsetting sections of the Mid-Atlantic Ridge.