普通法系（英语：Common Law；Common中文翻译为「普通」，是取其「普遍通行」之意），又称英美法系或海洋法系。该法系与欧陆法系（又称「大陆法」）并称为当今世界最主要的两大法系。特点就是判例法，即反复参考判决先例（precedent），最终产生类似道德观念一般的普遍的、约定俗成的法律（customary rules）。

普通法起源于中世纪的英格兰，世界人口的1/3（约23亿人）生活在普通法司法管辖区或混合民法系统中。

Common law (also known as case law or precedent) is law developed by judges, courts, and similar tribunals, stated in decisions that nominally decide individual cases but that in addition have precedential effect on future cases. Common law is a third branch of law, in contrast to and on equal footing with statutes which are adopted through the legislative process, and regulations which are promulgated by the executive branch.