Admiral is a four-star commissioned officer rank in the United States Navy, the United States Coast Guard, and the United States Public Health Service Commissioned Corps with the pay grade of O-10. Admiral ranks above vice admiral and below fleet admiral in the Navy; the Coast Guard and the Public Health Service do not have an established grade above admiral. Admiral is equivalent to the rank of general in the other uniformed services. The National Oceanic and Atmospheric Administration Commissioned Officer Corps has never had an officer hold the grade of admiral. However, 37 U.S.C. § 201 of the U.S. Code established the grade for the NOAA Corps, in case a position is created that merits the four-star grade.

Admiral of the Navy was the highest-possible rank in the United States Navy, prior to the creation of fleet admiral in 1944. The rank is considered to be at least equivalent to that of a five-star admiral, with Admiral George Dewey being the only officer to be appointed to the rank.