Islamically, حج is واجب (fard) only for those who have reached puberty (bulugh), are of sound mind, and meet other conditions of obligation. A child who has not reached puberty can perform حج, and it is valid as a voluntary (nafl) act of worship, but it does not count as fulfilling the واجب حج — they must perform حج again after reaching puberty. نبی کریم Muhammad (صلی اللہ علیہ وسلم) confirmed this when a woman lifted her child and asked if the child could perform حج.
Saudi Arabia sets its own administrative requirements which may include minimum ages for visa issuance. Children must be accompanied by parents or legal guardians and should be included in the family's حج application. Some countries have their own age restrictions for حج registration.
There is no maximum age limit in Islamic law for حج. However, Saudi authorities may issue health advisories or guidelines for elderly حجاج. Elderly individuals should obtain thorough medical clearance before applying. If a person is too old or ill to perform حج themselves, they may delegate someone to perform حج on their behalf (حج badal), provided they have the financial means. This proxy must have already performed their own واجب حج first.