An interest that does not take effect until a condition (contingency) has been met. When the condition is met, the interest becomes a vested interest.

Wills and trusts often include interests that are contingent on reaching a certain age or on surviving another person. For example, Adam dies and leaves his estate to his son Brian absolutely, provided Brian reaches the age of 21. Brian has a contingent interest in his father's estate. On his 21st birthday, his interest vests and he gets the estate outright.