Watch winders are mechanical devices that keep an automatic or self-winding watch operating smoothly. Certain types of timepieces do not need to be wound by turning a dial because they wind themselves when they are strapped to an arm that is swinging and twisting all day long. Winders are able to simulate that natural motion for those who don't wear their watch everyday.

The internal parts of automatic watches are designed to follow the pull of gravity. They don't have gears that must be wound with a spring, but instead, their tiny weights get pulled by gravity as the wearer moves and swings his arm. Little by little, these weights are twisting around both clockwise and counter-clockwise, until the watch is wound up. This type is considered automatic or self-winding, as opposed to quartz, kinetic, or mechanical watches.

People who own fancy, collectible, beloved, or merely sufficient self-winding watches may want to invest in a winder. Not only do these devices keep the timepiece accurate even when it's not being worn, they probably extend its overall life by keeping parts lubricated and moving. By advancing the mainspring, it gently and continually winds the watch, yet prevents it from ever being "overwound." Another mechanism inside most watches will disengage after the gears have been fully powered.