William D. Leahy
At the time of her retirement, she was the oldest active-duty commissioned officer in the United States Navy (79 years, eight months and five days), and had her retirement ceremony aboard the oldest commissioned ship in the United States Navy (188 years, nine months and 23 days). Admirals William D. Leahy, Chester W. Nimitz, Hyman G. Rickover and Charles Stewart were the only other officers in the Navy's history to serve on active duty at a higher age. Leahy and Nimitz served on active duty for life due to their promotions to the rank of fleet admiral.