英国政府行政机构是英国境内，直属某政府部门的次级自治公共机构；负责运行所属部门指示的专长政策。 英国境内的行政代理机构；分别向向英国(中央)政府、英国国会负责，其余向已权力下放的苏格兰政府、威尔斯议会政府、及北爱尔兰行政院负责。

每个行政机构由一名行政总裁率领，署理机构内日常运作。

行政机构的模式在1988年由首相柴契尔夫人的效率顾问Sir Robin Ibbs的报告上提出，此报告并猛烈评击已中央集权化的英国公务员队伍管理，只着重实施短期政策，而忽略交付；政府出现严重公共行政管理人才等问题。 同一报告上的首要解决办法，是成立数个由行政总裁率领集中在交付政策的行政机构。 首个行政机构，车辆检查处（the Vehicle Inspectorate），在1988年八月成立。

An executive agency is a part of a government department that is treated as managerially and budgetarily separate, to carry-out some part of the executive functions of the United Kingdom government, Scottish Government, Welsh Government or Northern Ireland Executive. Executive agencies are "machinery of government" devices distinct both from non-ministerial government departments and non-departmental public bodies (or "quangos"), each of which enjoy a real legal and constitutional separation from ministerial control. The model was also applied in several other countries.