Charlie is a common male nickname in English-speaking countries, usually short for Charles. It is occasionally found as a female nickname (usually spelt "Charley") as a shortened form of Charlotte.
Charlie represents the letter C in the NATO phonetic alphabet and the FAA aviation phonetic letters.
Charlie was a Vietnam War-era nickname for the Viet Cong, a shortening of "Victor Charlie," applied to the Viet Cong using the NATO phonetic alphabet.
Charlie is the NATO designation for a class of Soviet Navy submarines. The name comes from the NATO phonetic alphabet.