The general rule: A will requires legal capacity—typically age 18+ and sound mind (understanding what a will is, what you own, and who your natural beneficiaries are). Many states follow the Uniform Probate Code’s standard: “An individual 18 or more years of age who is of sound mind may make a will.” Massachusetts General Court

Example (Arizona): State law says, “A person who is eighteen years of age or older and who is of sound mind may make a will.” Arizona Legislature

Exceptions exist: Some states carve out narrow exceptions for emancipated, married, or military minors. (For example, Texas law recognizes under-18 capacity in specific circumstances such as lawful marriage or active military service.) Texas Statutes

Bottom line: If you’re 18+ and of sound mind, you can generally execute a will; if under 18, ask a licensed attorney about your state’s specific rules (and whether alternatives like beneficiary designations or trusts are appropriate).

Not legal advice. Laws vary by state; consult an attorney to confirm your options.