The rule against perpetuities is a rule in property law which prohibits a contingent grant or will from vesting outside a certain period. If there is a possibility of the estate vesting outside of the period, regardless of how remote that chance may be, the whole interest is void, and is stricken from a grant. The rule is concerned with the utility of property and tries to prevent people from tying up assets for too long a period of time—a concept often referred to as control by the "dead hand" or "mortmain." That is, the purpose is to "limit the testator's power to earmark gifts for remote descendants." The rule was enacted to prevent the concentration of wealth in society. When a part of a grant or will violates the Rule, only that portion of the grant or devise is removed; all other parts that do not violate the Rule are still valid conveyances of property.

Although most discussions and analysis relating to rule revolve around wills and trusts, the rule applies to any future dispositions of property, including (for example) options.