美国海军部依据美国国会法案创建于1798年4月30日，其担负的职能有：为美国海军以及美国海军陆战队提供行政管理、技术支持，并通过文官领导这两个军种（在国会或者总统授权下还领导美国海岸警卫队）。该部由海军部长领导，在海军中代号为SECNAV。海军部长由一名海军副部长辅佐。直至1947年国家军事机构成立以前，该部与美国战争部（当时陆军就隶属美国战争部，空军没有独立成军，隶属美国陆军）的部长为美国内阁成员。之后，国家军事机构于1949年更名为国防部。从而使海军部成为国防部的一个分支。

该部由主要位于五角大楼的行政部门以及邻近的海军附属建筑构成，并负责海军以及海军陆战队的士兵以及文职人员征召、组织、后勤、装备、训练、部署、召回及其人力资源和实物资产。该部还对海军舰艇、飞机、装备以及设施的建造、列装以及维护工作进行监督。

The United States Department of the Navy (DoN) was established by an Act of Congress on April 30, 1798 (initiated by the recommendation of James McHenry), to provide a government organizational structure to the United States Navy, the United States Marine Corps (from 1834 onward) and, when directed by the President (or Congress during time of war), the United States Coast Guard, as a service within the Navy, though each remain independent service branches. The Department of the Navy was an Executive Department and the Secretary of the Navy was a member of the President's cabinet until 1949, when amendments to the National Security Act of 1947 changed the name of the National Military Establishment to the Department of Defense and made it an Executive Department. The Department of the Navy then became, along with the Department of the Army and Department of the Air Force, a Military Department within the Department of Defense: subject to the authority, direction and control of the Secretary of Defense.