Islamically, Haji is wajib (fardhu) 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 Haji, and it is valid as a voluntary (nafl) act of worship, but it does not count as fulfilling the wajib Haji — they must perform Haji again after reaching puberty. Nabi Muhammad (shallallahu alaihi wa sallam) confirmed this when a woman lifted her child and asked if the child could perform Haji.
Arab Saudi 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 Haji application. Some countries have their own age restrictions for Haji registration.
There is no maximum age limit in Islamic law for Haji. However, Saudi authorities may issue health advisories or guidelines for elderly jamaah haji. Elderly individuals should obtain thorough medical clearance before applying. If a person is too old or ill to perform Haji themselves, they may delegate someone to perform Haji on their behalf (Haji badal), provided they have the financial means. This proxy must have already performed their own wajib Haji first.