The Constitution never uses the word "privacy." So where does the right come from? One major answer: the Ninth Amendment, which reads, "The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people." In plain English: just because the Constitution lists specific rights does not mean those are the only rights you have.
Justice Arthur Goldberg made this argument forcefully in his concurrence in Griswold v. Connecticut (1965), where the Court struck down a state ban on contraceptives. Goldberg wrote that the Ninth Amendment shows the Framers believed fundamental rights exist beyond the ones they wrote down -- and that marital privacy is one of them. He argued the Ninth Amendment alone was enough to find a right to privacy without needing other amendments. This matters far beyond contraception. The Ninth Amendment's logic undergirds debates over medical decisions, personal data, and digital surveillance. When tech companies collect your location data or governments demand access to your encrypted messages, the question is the same one Goldberg raised in 1965: do Americans retain fundamental rights the Founders never bothered to list? The Ninth Amendment says yes.