William Frank Szymczyk (/ˈsɪmzɪk/; born February 13, 1943) is an American music producer and technical engineer best known for working with rock and blues musicians, most notably the Eagles in the 1970s. He produced many top albums and singles of the 1970s, though he retired from the music business by 1990. He re-emerged in the late 2000s, taking on select projects including the 2007 Eagles album Long Road Out of Eden and the 2008 eponymous debut of Brian Vander Ark.
Unlike many music producers, Szymczyk has no background as a musician. He was originally a sonar operator for the U.S. Navy and took some audio production classes as part of his Navy training. Besides his work with the Eagles, he has produced hit songs and albums for such diverse artists as B.B. King, Joe Walsh, The James Gang, and Elvin Bishop.