曼纳海姆防线（芬兰文：Mannerheim-linja）是芬兰建造于卡累利阿地峡（Karelian Isthmus）用来防御苏联的防御工事。

芬兰花了10年建设，成功将曼纳海姆防线建造成完整的防御工事体系。它由纵深约90公里的3道防御地带组成，各道防御地带配合著沼泽湖泊等天然障碍物兴建，构筑有670个固定发射工事和土木质火力点，另有近800个地下暗堡，并以交通壕连接。在主要防御地带前设有20～60公里纵深的缓冲地带。主要防御地带前和缓冲地带内广泛设置了反坦克和反步兵地雷和反坦克桩砦、反坦克壕和反坦克崖壁。

The Mannerheim Line (Finnish:Mannerheim-linja, Swedish:Mannerheimlinjen) was a defensive fortification line on the Karelian Isthmus built by Finland against the Soviet Union. During the Winter War it became known as the Mannerheim Line, after Field Marshal Baron Carl Gustaf Emil Mannerheim. The line was constructed in two phases: 1920–1924 and 1932–1939. By November 1939, when the Winter War began, the line was by no means complete.