This article analyzes the rights and obligations of co-owners of copyrights. Co-ownership of a copyright may result from the initial creation of the work by more than one author. Copyright law refers to that as “joint authorship” or a “joint work.” It may also result from ordinary property law. A married person in a community property state holds any copyright newly issued during the marriage as community property. Likewise, a copyright acquired with community funds will be held as community property. Co-ownership of a copyright can also occur in the usual ways in which property is transferred to more than one person: by sale, gift, will, intestate succession, or as part of a property settlement on divorce. This author believes that a large number of copyright co-ownerships result from community property, divorce, or estate planning by the copyright holder or her or his successor(s), rather than from joint authorship.