A hatter is someone who makes or sells hats. In the 1800s and early 1900s, hatters were skilled craftspeople who shaped felt, straw, and fabric into the many styles of hats that nearly everyone wore daily. Men might wear bowlers, top hats, or fedoras, while women wore bonnets, cloches, or wide-brimmed sun hats.

The phrase mad as a hatter comes from a tragic reality of the hatmaking trade. Hatters used mercury, a toxic metal, to treat felt, and breathing mercury fumes over years caused tremors, confusion, and erratic behavior. People noticed that hatters sometimes seemed strange or “mad,” not realizing the work itself was poisoning them. Lewis Carroll made the phrase famous with the Mad Hatter character in Alice's Adventures in Wonderland.

Today, few people wear hats regularly, so hatters are less common than they once were. Those who remain often create custom hats for special occasions, theater productions, or historical reenactments. Modern hatters use safe materials and methods, so the connection between hatmaking and madness is purely historical.