Jonathan William Greenert is a former United States Navy admiral who served as the 30th Chief of Naval Operations from September 23, 2011, to September 18, 2015. He previously served as the 36th Vice Chief of Naval Operations from August 13, 2009, to August 22, 2011. Prior to that, he served as Commander, U.S. Fleet Forces Command from September 29, 2007, to July 29, 2009, deputy chief of Naval Operations for Integration of Capabilities and Resources from September 2006 to September 2007, and commander of U.S. Seventh Fleet from August 2004 to September 2006. He retired from the navy after over 40 years of service. In March 2016, the National Bureau of Asian Research announced that Greenert would become the third holder of the John M. Shalikashvili Chair in National Security Studies at NBR. In April 2016, Greenert was appointed to the board of directors for BAE Systems for a three-year term.

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.