A concurrent estate or co-tenancy is a concept in property law, particularly derived from the common law of real property, which describes the various ways in which property can be owned by more than one person at a given time. If more than one person own the same property, they are referred to as co-owners, co-tenants or joint tenants. Most common law jurisdictions recognize tenancies in common and joint tenancies, and some also recognize tenancies by the entirety. Many jurisdictions refer to a joint tenancy as a joint tenancy with right of survivorship, and a few U.S. States treat the phrase joint tenancy as synonymous with a tenancy in common.

The type of ownership determines the rights of the parties to sell their interest in the property to others, to will the property to their devisees, or to sever their joint ownership of the property. Just as each of these affords a different set of rights and responsibilities to the co-owners of property, each requires a different set of conditions in order to exist.