Collar stays (sometimes known as collar thingies, collar sticks, bones, knuckles, tabs, in the UK, collar stiffeners, and in Eastern Canada collar stiffs) are shirt accessories.

Collar stays are smooth, rigid strips of metal (such as brass, stainless steel, or sterling silver), horn, baleen, mother of pearl, or plastic, rounded at one end and pointed at the other, inserted into specially made pockets on the underside of a shirt collar to stabilize the collar's points. The stays ensure that the collar lies flat against the collarbone, looking crisp and remaining in the correct place. Often shirts come with plastic stays which may eventually need to be replaced if they bend; metal replacements do not have this problem.