Lieutenant General

A Lieutenant General ranks immediately below a General and above a Major General.
In the US Army, Marine Corps and Airforce a Lieutenant General is a three-star General. For insignia in the British Army see General.
A Lieutenant General is equivalent to a Vice Admiral in both the US Navy and Royal Navy. Its equivalent rank the the Royal Air Force and airforces of many Commonwealth countries is Air Marshal
See also: wiktionary definition of and Comparative military ranks.