里海（，波斯语：دریای مازندران/دریای خزر‎，俄语：Каспийское море，哈萨克语：Каспий теңізі，土库曼语：Hazar deňizi）位于亚洲与欧洲交界，是世界上面积最大的封闭内陆水体，同时也是世界上最大的湖泊以及内陆海。里海的面积有37万1000平方公里（不包括卡腊博加兹哥耳湾)，体积为7万8200立方公里，最深处有1,025米（3,360英尺），平均深度为187米（610英尺）。里海是一个内流湖，没有流出口，被多个国家环抱，西北的国家是俄罗斯，西面是阿塞拜疆，南面是伊朗，东南是土库曼斯坦，东北为哈萨克斯坦。

The Caspian Sea is the largest enclosed inland body of water on Earth by area, variously classed as the world's largest lake or a full-fledged sea. It is in an endorheic basin (it has no outflows) located between Europe and Asia. It is bounded to the northeast by Kazakhstan, to the northwest by Russia, to the west by Azerbaijan, to the south by Iran, and to the southeast by Turkmenistan.