In a BDSM context, a collar is a device of any material placed around the neck of the submissive partner. It is also a term used to show ownership of one partner by another. A person wearing a collar to symbolize their relationship with another is said to be collared. Some people conduct formal "collaring ceremonies," which are regarded as effectively solemnizing their relationship in a similar way as a marriage ceremony. The standard form of a collar is a black leather band around the neck and often has metal D-rings added to allow the attachment of a leash.

Collars may be used in role-playing games involving humiliation because they have connotations of control and pet-like status, especially when worn with a leash.