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.

The parties who own property jointly are referred to as co-tenants or joint tenants. Most common-law jurisdictions recognize three kinds of concurrent estate: tenancy in common, joint tenancy with right of survivorship, and tenancy by the entirety. Many jurisdictions simply refer to a joint tenancy with right of survivorship as a joint tenancy, but 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 convey 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 joint owners of property, each requires a different set of conditions in order to exist.