Max Carl Gronenthal is an American rock singer, keyboardist, guitarist and songwriter. He is the co-lead singer of the classic rock band Grand Funk Railroad. In addition, he spent several years as the keyboardist and lead singer for the southern rock band 38 Special. Carl is known for having co-written and sung lead vocals on 38 Special's hit song, "Second Chance" (1989).

38 Special, often stylized as .38 Special or spelled out as Thirty-eight Special, is an American rock band formed by singer-guitarists Donnie Van Zant and Don Barnes in Jacksonville, Florida, in 1974.