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