Incorporation of the Bill of Rights is the legal doctrine by which the U.S. Bill of Rights, either in full or in part, is applied to the states through the Due Process Clause of the Fourteenth Amendment.

While it is necessarily impossible to gauge the intention of all the framers (and all the ratifiers) of the Fourteenth Amendment, there is substantial evidence—i.e., from the Congressional Globe—about the intentions of John Bingham, the principal framer of the Amendment. Bingham stated many times that the Fourteenth Amendment would enforce the Bill of Rights against state governments.

Though the Bill of Rights was originally written to limit only the power of the federal government, the Supreme Court has ruled that most of its guarantees protect citizens against state governments. Because the Slaughterhouse Cases of 1872 found only a very limited number of privileges inherent in federal citizenship, the Privileges or Immunities Clause of the Fourteenth Amendment has not been used to incorporate the Bill of Rights. This has left the Due Process Clause as the only means by which this can be effected.

The genesis of incorporation has been traced back to either Chicago, Burlington & Quincy Railway Co. v. Chicago (1897) in which the Supreme Court appeared to require some form of just compensation for property appropriated by state or local authorities (although there was a state statute on the books that provided the same guarantee) or, more commonly, to Gitlow v. New York (1925), in which the Court expressly held that States were bound to observe First Amendment free speech protections. Since that time, the Court has steadily incorporated most of the significant provisions of the Bill of Rights. Exceptions are the Fifth Amendment right to an indictment by a grand jury, the Seventh Amendment right to a jury trial in civil lawsuits, which have been ruled to only apply in federal courts, and the Sixth Amendment's implicit command that a criminal jury can consist only of twelve members and must reach a unanimous verdict.

Many of the provisions of the First Amendment were applied to the States in the 1930s and 1940s, but most of the procedural protections provided to criminal defendants were not enforced against the States until the Warren Court of the 1960s, famous for its concern for the rights of those accused of crimes, brought state standards in line with federal requirements.

As the incorporation drive picked up speed in the 1940s and '50s, disagreements over the method that ought to be taken in making Bill of Rights guarantees enforceable to the States emerged. One school of thought, championed by Justice Hugo Black, was total incorporation. Black felt that the Fourteenth Amendment required that the States respect all of the enumerated rights set forth in the first ten amendments, but did not wish to see the doctrine expanded to include other, unenumerated "fundamental rights." Black felt that his formulation eliminated any arbitrariness or caprice in deciding what the Fourteenth Amendment ought to protect, by sticking to words already to be found in the Constitution. Justice Felix Frankfurter, however, felt that the incorporation process ought to be incremental, and that the federal courts should only apply those sections of the Bill of Rights whose abridgement would "shock the conscience," as he put it in Rochin v. California (1952). Although Frankfurter's incrementalist approach did carry the day, the end result is very nearly what Justice Black advocated, with the exceptions noted above.

It should be noted that incorporation applies both procedural and substantive guarantees to the states. Thus, procedurally, only a jury can convict a defendant of a serious crime, since the Sixth Amendment jury-trial right has been incorporated against the states; substantively, for example, States must recognize the First Amendment prohibition against a state-established religion, regardless of whether State laws and constitutions offer such a prohibition. There are, however, some substantive guarantees whose incorporation the Supreme Court has not yet ruled on—for example, the Second Amendment right to bear arms, and the Eighth Amendment prohibition on excessive bail and fines.