What underwear did ladies have beneath their Regency gowns? Generally, not much. I’ve blogged before about see-through gowns and the Regency petticoat but what else was underneath?
The go-to reference book for underwear is The History of Underclothes by C. Willet and Phillis Cunnington which starts at the medieval period and finishes at 1939. 
As you can see from the cover, it includes corsets and bustles and much, much more. And it includes underwear for men. That gent in the middle of the cover is wearing a Jaeger nightgown, dating from the early 1880s.
The lady to his right is wearing “cami-knickers in crêpe-de-chine” from 1922. (No, they didn’t look like knickers to me either!) The lady to his left is much earlier, of course. She may look fully dressed, but she isn’t. That’s corset, chemise and underskirt, dating from about 1780. And French!
