内阁是政府高级官员代表政府各部门商议政策的行政机构。

内阁的中文词源来自明朝，但作为现代国家机构的用法则源自英国。

在英国历史上，内阁是秘密议会的继承者。现在内阁的理念一般相信源自英国国王乔治一世和乔治二世；乔治一世来自德意志，故英文不甚流利，于是敕命辉格党领袖华波尔爵士（Sir Robert Walpole）为内阁首领，为国王主持军政会议，也成为了内阁首相制度的滥觞。

现在大部份国家都采用了这种制度，就算是非英语用户，对英国政治陌生的人也因而非常依赖这种顾问团体。

大明开国皇帝朱元璋执政期间，因担心丞相胡惟庸相权权力过大而架空君权，决定以谋反罪名废相，之后明成祖设内阁置大学士作为秘书兼顾问组织代之，本意为将其权力降低，事实上由于皇帝的信任，居首位的大学士（首辅）权力可以与宰相相比，于明宪宗成化（1465年—1487年）首辅制臻至成熟；历代著名的大学士包括杨廷和、夏言、严嵩、徐阶、张居正等。至清代时其权力始消减，部分首辅权力转移至总督均分，而自雍正帝后，军机处取代了内阁在政治决策上的地位。晚清立宪运动后，于1911年创建中国第一个现代意义的内阁——庆亲王内阁。

A cabinet is a body of high-ranking state officials, typically consisting of the top leaders of the executive branch. They are usually called ministers, but in some jurisdictions are sometimes called Secretaries.

The functions of a cabinet are varied: in some countries it is a collegial decision-making body with collective responsibility, while in others it may function either as a purely advisory body or an assisting institution to a decision making head of state or head of government. In some countries, the cabinet is called "Council of Ministers" or "Government Council" or lesser known names such as "Federal Council" (in Switzerland), "Inner Council" or "High Council". These countries may differ in the way that the cabinet is used or established.