不可抗力（英语：Force majeure）是法律术语，一项免责条款，解作一种人们不能预见、不可避免、不能克服的自然、社会现象客观情况。自然现象包括但不限于天灾人祸如地震、台风、洪水和海啸；社会现象则包括但不限于战争、市政工程建设和其它政府政策。

在很多情况中，合约中也会列明如因不可抗力的发生而阻碍卖方的交货义务或履行合约，违约方可部分或者全部免除违约责任。

Force majeure (/ˌfɔːrs/ FORS, /ˌfɔərs mɑːˈʒɜːr/ mah-ZHUR, or /məˈʒɜːr/ mə-ZHUR; French pronunciation: ​[fɔʁs maʒœʁ]) – or vis major (Latin) – meaning "superior force", also known as cas fortuit (French) or casus fortuitus (Latin) "chance occurrence, unavoidable accident", is a common clause in contracts that essentially frees both parties from liability or obligation when an extraordinary event or circumstance beyond the control of the parties, such as a war, strike, riot, crime, or an event described by the legal term act of God (hurricane, flood, earthquake, volcanic eruption, etc.), prevents one or both parties from fulfilling their obligations under the contract. In practice, most force majeure clauses do not excuse a party's non-performance entirely, but only suspend it for the duration of the force majeure.