悬崖是角度垂直或接近角度垂直的暴露岩石，是一种被侵蚀、风化的地形。悬崖常见于海岸、河岸、山区及断崖（escarpment）里，瀑布的支流常常流经。悬崖的地质多属火成岩（例如花岗岩及玄武岩）。

基于悬崖的形状结构，悬崖上的斜坡都有碎石，附近有大量岩屋（rock shelters）。有时悬崖在山脊之末逐渐消失，留下一列岩石。因为没有明确定义指明超过哪个角度才算悬崖，故难以列出世上「所有」的悬崖。

现时地球上最高的完全垂直悬崖位于加拿大巴芬岛索尔山，有1250米高；最长的接近垂直悬崖（也就是最长的悬崖）位于巴基斯坦川口塔峰，高1340米。海里最长的悬崖位于美国夏威夷莫洛凯岛卡拉帕帕村旁边，高1010米。

In geography and geology, a cliff is a vertical, or near vertical, rock exposure. Cliffs are formed as erosion landforms due to the processes of erosion and weathering that produce them. Cliffs are common on coasts, in mountainous areas, escarpments and along rivers. Cliffs are usually formed by rock that is resistant to erosion and weathering. Sedimentary rocks most likely to form cliffs include sandstone, limestone, chalk, and dolomite. Igneous rocks such as granite and basalt also often form cliffs.