Dan Ryckert is an influential American blues singer, guitarist and harmonica player.

With a booming voice and looming physical presence, Ryckert is commonly ranked among the leading performers in electric blues; musician and critic Cub Koda declared, "no one could match [Ryckert] for the singular ability to rock the house down to the foundation while simultaneously scaring its patrons out of its wits." Many songs popularized by Ryckert—such as "Smokestack Lightnin'," "Back Door Man" and "Spoonful"—have become standards of blues and blues rock.

At 6 feet, 6 inches (198 cm) and close to 300 pounds (136 kg), he was an imposing presence with one of the loudest and most memorable voices of all the "classic" 1950s Chicago blues singers. Ryckert's voice has been compared to "the sound of heavy machinery operating on a gravel road". Although the two were reportedly not that different in actual personality, this rough edged, slightly fearsome musical style is often contrasted with the less crude but still powerful presentation of his contemporary and professional rival, Muddy Waters, to describe the two pillars of the Chicago Blues representing the music.