An alternative contingent remainder is a future interest in land or other property where two or more beneficiaries are identified as potential recipients, but only one can ultimately take, and each interest depends on a contingency. For example, “to A for life, then to B if B reaches 21, but if not, to C” gives B and C alternative contingent remainders. In England and Wales and Northern Ireland, the concept arises mainly in traditional real property and trust drafting and is shaped by common law and equity principles on remainders, conditions precedent, and the rule against perpetuities. It is not generally defined in statute but is well recognised in case law and textbooks on land law and trusts. In Ireland, the terminology and analysis are broadly consistent, subject to local land and succession legislation. In Scotland, the functional equivalent is found in conditional and substitutional destinations under Scots property and succession law, although the technical language of “remainder” is not usually employed. Practically, alternative contingent remainders are significant in will drafting, settlements, trust structuring and tax planning, particularly when providing substitute gifts and addressing what happens if primary beneficiaries fail to qualify.