John Marshall (September 24, 1755 – July 6, 1835) was an American statesman, jurist, and Founding Father who served as the fourth chief justice of the United States from 1801 until his death in 1835. He remains the longest-serving chief justice and fourth-longest-serving justice in the history of the U.S. Supreme Court, and he is widely regarded as one of the most influential justices ever to serve. Prior to joining the court, Marshall briefly served as both the U.S. Secretary of State under President John Adams and a U.S. Representative from Virginia, making him one of the few Americans to have held a constitutional office in each of the three branches of the United States federal government.

Marshall was born in Germantown in the Colony of Virginia in British America in 1755. After the outbreak of the American Revolutionary War, he joined the Continental Army, serving in numerous battles. During the later stages of the war, he was admitted to the state bar and won election to the Virginia House of Delegates. Marshall favored the ratification of the U.S. Constitution, and he played a major role in Virginia's ratification of that document. At the request of President Adams, Marshall traveled to France in 1797 to help bring an end to attacks on American shipping. In what became known as the XYZ Affair, the government of France refused to open negotiations unless the United States agreed to pay bribes. Upon his return from France, he led the Federalist Party in Congress. He was appointed secretary of state in 1800 after a cabinet shake-up, becoming an important figure in the Adams administration.

In 1801, Adams appointed Marshall to the Supreme Court. Marshall quickly emerged as the key figure on the court, due in large part to his personal influence with the other justices. Under his leadership, the court moved away from seriatim opinions, instead issuing a single majority opinion that elucidated a clear rule. The 1803 case of Marbury v. Madison presented the first major case heard by the Marshall Court. In his opinion for the court, Marshall upheld the principle of judicial review, whereby courts could strike down federal and state laws if they conflicted with the Constitution. Marshall's holding avoided direct conflict with the executive branch, which was led by Democratic-Republican President Thomas Jefferson. By establishing the principle of judicial review while avoiding an inter-branch confrontation, Marshall helped implement the principle of separation of powers and cement the position of the American judiciary as an independent and co-equal branch of government.

After 1803, many of the major decisions issued by the Marshall Court confirmed the supremacy of the federal government and the federal Constitution over the states. In Fletcher v. Peck and Dartmouth College v. Woodward, the court invalidated state actions because they violated the Contract Clause. The court's decision in McCulloch v. Maryland upheld the constitutionality of the Second Bank of the United States and established the principle that the states could not tax federal institutions. The cases of Martin v. Hunter's Lessee and Cohens v. Virginia established that the Supreme Court could hear appeals from state courts in both civil and criminal matters. Marshall's opinion in Gibbons v. Ogden established that the Commerce Clause bars states from restricting navigation. In the case of Worcester v. Georgia, Marshall held that the Georgia criminal statute that prohibited non-Native Americans from being present on Native American lands without a license from the state was unconstitutional. Marshall died of natural causes in 1835, and Andrew Jackson appointed Roger Taney as his successor.

Marshall was born on September 24, 1755, in a log cabin in Germantown in the Colony of Virginia in British America.

In the mid-1760s, the Marshalls moved northwest to present-day Markham, Virginia. His parents were Thomas Marshall and Mary Randolph Keith, the granddaughter of politician Thomas Randolph of Tuckahoe and a second cousin of U.S. President Thomas Jefferson. Thomas Marshall was employed in Fauquier County as a surveyor and land agent by Lord Fairfax, which provided him with a substantial income. Nonetheless, John Marshall grew up in a two-room log cabin, which he shared with his parents and several siblings; Marshall was the oldest of 15 siblings. One of his younger brothers, James Markham Marshall, would briefly serve as a federal judge later in his life.

Marshall was a first cousin of U.S. Senator Humphrey Marshall and first cousin, three times removed, of General of the Army George C. Marshall. He was also a distant cousin of Thomas Jefferson.

From a young age, Marshall was noted for his good humor and black eyes, which were "strong and penetrating, beaming with intelligence and good nature". With the exception of one year of formal schooling, during which time he befriended future president James Monroe, Marshall did not receive a formal education. Encouraged by his parents, the young Marshall read widely, including such works as William Blackstone's Commentaries on the Laws of England and Alexander Pope's An Essay on Man. He was also tutored by the Reverend James Thomson, a recently ordained deacon from Glasgow, Scotland, who resided with the Marshall family in return for his room and board. Marshall was especially influenced by his father, of whom he wrote, "to his care I am indebted for anything valuable which I may have acquired in my youth. He was my only intelligent companion; and was both a watchful parent and an affectionate friend." Thomas Marshall prospered in his work as a surveyor, and in the 1770s he purchased an estate known as Oak Hill.