Rational basis review is a standard of judicial review used by courts to evaluate the constitutionality of legislative classifications or government actions. It requires that the law or action in question is rationally related to a legitimate government interest, meaning the government does not need to provide a compelling reason for its action, just a plausible one. This standard often comes into play when examining laws that do not involve fundamental rights or suspect classifications, making it one of the most lenient forms of scrutiny in constitutional law.