is a narrowly defined tool in contact law that recognizes parties have not reached mutual agreement or meeting of the minds if they are mistaken about a material aspect of the transaction. The mistake must be unintentional and not due to negligence or ignorance. A contract based on mistake would be void. A party cannot claim "mistake" to get out of a contract he or she signed.

Example: A seller has a piece of land for sale. A potential buyer visits the area but views the wrong lot. After entering into the contract the mistake is discovered and the contract is considered void. Neither party could be forced to perform as there was no ‘meeting of the minds’.