The doctrine of incorporation is a legal doctrine developed by the United States Supreme Court. It is a legal theory based on the due process clause of the Fourteenth Amendment to the U.S. Constitution. The doctrine of incorporation is sometimes used in cases involving the Bill of Rights, which is the first 10 amendments to the U.S. Constitution. When applied, the doctrine of incorporation is used as the basis to require state governments to grant the same rights to their citizens as the federal government must under the Bill of Rights.

Until the creation of the doctrine of incorporation, the Bill of Rights applied only to the federal government. Although the Bill of Rights was ratified in 1791 and the Fourteenth Amendment in 1868, the doctrine of incorporation was not created until the 1890s. At that time, a series of cases were appealed to the Supreme Court that caused the Court to begin to interpret the due process clause of the Fourteenth Amendment in a broader way.

The broader interpretation was called the doctrine of incorporation. Under it, portions of the Bill of Rights were made enforceable against state governments for the first time. Over time, certain sections of the Bill of Rights were gradually identified and incorporated as falling under the Fourteenth Amendment’s guarantee of legal due process to all U.S. citizens. The doctrine of incorporation allowed the Supreme Court to say that the specific portion of the Bill of Rights in the case it was deciding also applied to the states, because the Fourteenth Amendment applied to the states.

Among the rights that states have been required to grant to their citizens under this doctrine are the First Amendment’s guarantees of freedom of religion, speech, the press and assembly. Also among the rights that states must grant are the Second Amendment’s right to keep and bear arms and the Third Amendment’s guarantee of freedom from the quartering of soldiers. In addition, the Fourth Amendment’s protection from unreasonable search and seizure and the requirement for warrants have been held to apply to the states.

States also are required to grant citizens protection from self-incrimination and double jeopardy under the Fifth Amendment. The Sixth Amendment's grants of the right to an attorney and a speedy, public trial by an impartial jury also are required of states following the application of the doctrine of incorporation. Finally, the Eighth Amendment’s protection from cruel and unusual punishment also must be granted by states.