The Pacific Squadron was part of the United States Navy squadron stationed in the Pacific Ocean in the 19th and early 20th centuries. Initially with no United States ports in the Pacific, they operated out of storeships which provided naval supplies and purchased food and obtained water from local ports of call in the Hawaiian Islands and towns on the Pacific Coast. Throughout the history of the Pacific Squadron, American ships fought against several enemies. Over one-half of the United States Navy would be sent to join the Pacific Squadron during the Mexican–American War. During the American Civil War, the squadron was reduced in size when its vessels were reassigned to Atlantic duty. When the Civil War was over, the squadron was reinforced again until being disbanded just after the turn of the 20th century.

The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the world's most powerful navy and the largest by tonnage, at 4.5 million tons in 2021 and in 2009 an estimated battle fleet tonnage that exceeded the next 13 navies combined. It has the world's largest aircraft carrier fleet, with 11 in service, 1 undergoing trials, two new carriers under construction, and six other carriers planned as of 2024. With 336,978 personnel on active duty and 101,583 in the Ready Reserve, the U.S. Navy is the third largest of the United States military service branches in terms of personnel. It has 299 deployable combat vessels and about 4,012 operational aircraft as of July 18, 2023.