恐怖平衡（Balance of terror）主要是指在冷战时期，美国及苏联的核武竞赛。

恐怖平衡是指二国之间都有大量核子武器，足以造成全球性的核战争，在此情形下产生的脆弱和平。这句话最早可能是由加拿大总理莱斯特·皮尔逊在1955年6月提出，他在联合国宪章签署十周年时提及：「恐怖平衡已经取代了各国之间的权力平衡。」

有些政治学者用此一词语来描述第二次世界大战前后，国际情势的差异。在二次大战前，各国避免战争的方式是在其（经济、政治及军事）实力上设法维持平衡，权力平衡或势力均衡一般也是描述此一阶段产生的和平。

The phrase "balance of terror" is usually, but not invariably, used in reference to the nuclear arms race between the United States and the Soviet Union during the Cold War.

It describes the tenuous peace that existed between the two countries as a result of both governments being terrified at the prospect of a world-destroying nuclear war. The term is usually used for rhetorical purposes, and was probably coined by Lester Pearson in June 1955 at the 10th anniversary of the signing of the UN Charter: "the balance of terror has replaced the balance of power".