United States Naval Reserve (Women's Reserve), better known as the WAVES (for Women Accepted for Volunteer Emergency Service), was the women's branch of the United States Naval Reserve during World War II. It was established on July 21, 1942, by the U.S. Congress and signed into law by President Franklin D. Roosevelt on July 30. This authorized the U.S. Navy to accept women into the Naval Reserve as commissioned officers and at the enlisted level, effective for the duration of the war plus six months. The purpose of the law was to release officers and men for sea duty and replace them with women in shore establishments. Mildred H. McAfee, on leave as president of Wellesley College, became the first director of the WAVES. She was commissioned a lieutenant commander on August 3, 1942, and later promoted to commander and then to captain.

The notion of women serving in the Navy was not widely supported in the Congress or by the Navy, even though some of the lawmakers and naval personnel did support the need for uniformed women during World War II. Public Law 689, allowing women to serve in the Navy, was due in large measure to the efforts of the Navy's Women's Advisory Council, Margaret Chung, and Eleanor Roosevelt, the first lady of the United States.

To be eligible for officer candidate school, women had to be aged 20 to 49 and possess a college degree or have two years of college and two years of equivalent professional or business experience. Volunteers at the enlisted level had to be aged 20 to 35 and possess a high school or a business diploma, or have equivalent experience. The WAVES were primarily white, but 72 African-American women eventually served. The Navy's training of most WAVES officer candidates took place at Smith College, Northampton, Massachusetts. Specialized training for officers was conducted on several college campuses and naval facilities. Most enlisted members received recruit training at Hunter College, in the Bronx, New York City. After recruit training, some women attended specialized training courses on college campuses and at naval facilities.

The WAVES served at 900 stations in the United States. The territory of Hawaii was the only overseas station where their staff was assigned. Many female officers entered fields previously held by men, such as medicine and engineering. Enlisted women served in jobs from clerical to parachute riggers. Many women experienced workplace hostility from their male counterparts. The Navy's lack of clear-cut policies, early on, was the source of many of the difficulties. The WAVES' peak strength was 86,291 members. Upon demobilization of the officer and enlisted members, Secretary of the Navy James Forrestal, Fleet Admiral Ernest King, and Fleet Admiral Chester Nimitz all commended the WAVES for their contributions to the war effort.

In May 1941, Representative Edith Nourse Rogers of Massachusetts introduced a bill in the U.S. Congress to establish a Women's Army Auxiliary Corps (WAAC). As auxiliaries, women would serve with the Army rather than in it, and they would be denied the benefits of their male counterparts. Opposition delayed the passage of the bill until May 1942. At the same time, the U.S. Navy's Bureau of Aeronautics felt the Navy would eventually need women in uniform and had asked the Bureau of Naval Personnel, headed by Rear Admiral Chester W. Nimitz, to propose legislation as it had done during World War I, authorizing women to serve in the Navy under the Yeoman (F) classification. Nimitz was not considered an advocate for bringing women into the Navy, and the head of the U.S. Naval Reserve expressed the view that the Civil Service would be able to supply any extra personnel that might be needed.

On December 9, 1941, Representative Rogers telephoned Nimitz and asked him whether the Navy was interested in some sort of women's auxiliary corps. In her book Lady in the Navy, Joy Bright Hancock quotes his reply: "I advised Mrs. Rogers that at the present time I saw no great need for such a bill". Nevertheless, within days Nimitz was in touch with all Navy Department bureaus asking them to assess their needs for an equivalent to the WAAC. With few exceptions, the responses were negative, but Congressional inquiries about the Navy's plan for women continued to increase.

On January 2, 1942, the Bureau of Naval Personnel, in an about-face, recommended to Secretary of the Navy Frank Knox that Congress be asked to authorize a women's organization. The following month, Knox recommended a women's branch as part of the Naval Reserve. The director of the Bureau of the Budget opposed his idea, but would agree to legislation similar to the WAAC bill – where women were with, but not in, the Navy. This was unacceptable to Knox. The Bureau of Aeronautics continued to believe there was a place for women in the Navy, and appealed to an influential friend of naval aviation named Margaret Chung. A San Francisco physician and surgeon, Chung was known to have had an interest in naval aviation. Many of her naval friends referred to themselves as sons of Mom Chung. In Crossed Currents, the authors describe how Chung used her influence:

Having learned of the stalemate, she asked one of these [sons], Representative Melvin Maas of Minnesota, who had served in the aviation branch of the U.S. Marine Corps in World War I, to introduce legislation independently of the Navy. On 18 March 1942 he did just that.