John William "Billy" Mackel (December 28, 1912 – May 5, 1986) was an American jazz guitarist.Mackel played banjo early in his career in his home town of Baltimore, but switched to guitar (like many banjoists of the day) in the 1930s. He played left-handed. He led his own band early in the 1940s, then joined Lionel Hampton in 1944. Mackel worked with Hampton, with occasional intermissions, for over thirty years, touring and recording with him copiously.