High Quality Content by WIKIPEDIA articles! A third party beneficiary, in the law of contracts, is a person who may have the right to sue on a contract, despite not having originally been an active party to the contract. This right, known as a ius quaesitum tertio, arises where the third party (tertius or alteri) is the intended beneficiary of the contract, as opposed to an incidental beneficiary. It vests when the third party relies on or assents to the relationship, and gives the third party the right to sue either the promisor (promittens, or performing party) or the promisee (stipulans, or anchor party) of the contract, depending on the circumstances under which the relationship was created. A contract made in favor of a third party is known as a third-party contract or contract for the benefit of a third party (stipulatio alteri), and any action to enforce a ius quaesitum tertio is known as a third party action.