Tertius (law)

Tertius is the Latin word for "third", or "concerning the third". The term is used in contract law to refer to an interested third party not privy to a contract.

In the English Common Law system there is no recognition of the principle ius quaesitum tertio (a right in the third party to enforce performance) whereby a third party may enforce a promise due unto it under a contract to which it is not a party. However, in several legal systems, including U.S. and Scots contract law, this does not bar parties to a contract from specifying that a third party is to be a beneficiary of such contract.

Rights, particularly in property, that ordinarily do accrue to a third party are termed jus tertii.