Luther Martin (February 9, 1748-July 8, 1826) was a politician and one of United States' Founding Fathers, but refused to sign the Constitution because he felt it violated states' rights.

Like many of the delegates to the Constitutional Convention, Luther Martin attended the College of New Jersey (later Princeton), from which he graduated at the head of a class of 35 in 1746. Though born in Metuchen, New Jersey, in 1748, Martin moved to North Carolina after receiving his degree and taught there for three years. He then began to study the law and was admitted to the Virginia bar in 1771.

Martin played the violin and this was the single most important part of his childhood. Martin was an early advocate of American independence from Great Britain. In the fall of 1771 he served on the patriot committee of Somerset County, New Jersey, and in December he attended a convention of the Province of Maryland in Annapolis, which had been called to consider the recommendations of the Continental Congress. Maryland appointed Luther Martin its attorney general in early 1778. In this capacity, Martin vigorously prosecuted Loyalists, whose numbers were strong in many areas of the state. Tensions had even led to insurrection and open warfare in some counties. While still attorney general, Martin joined the Baltimore Light Dragoons. In July 1781 his unit joined Pierre Lafayette's forces near Fredericksburg, Virginia, but Martin was recalled by the governor to prosecute a treason trial.

From 1778 to 1805 he was Attorney General of Maryland; in 1814-1816 he was chief judge of the court of Oyer and Terminer for the city of Baltimore; and in 1818 to 1822 he was again attorney-general of Maryland. Martin married Maria Cresap on Christmas Day 1783. Of their five children, three daughters lived to adulthood. His postwar law practice grew to become one of the largest and most successful in the country. In 1785 Martin was elected to the Continental Congress, but this appointment was purely honorary. His numerous public and private duties prevented him from traveling to Philadelphia.

He attended the Constitutional Convention of 1787 at Philadelphia, but opposed the ratification of the United States Constitution and refused to affix his signature.

At the Constitutional Convention Martin opposed the idea of a strong central government. When he arrived on June 9, 1787, he expressed suspicion of the secrecy rule imposed on the proceedings. He consistently sided with the small states and voted against the Virginia Plan. On June 27 Martin spoke for more than three hours in opposition to the Virginia Plan's proposal for proportionate representation in both houses of the legislature. Martin served on the committee formed to seek a compromise on representation, where he supported the case for equal numbers of delegates in at least one house. Before the convention closed, he and another Maryland delegate, John Francis Mercer, walked out.

In an address to the Maryland House of Delegates in 1787 and in numerous newspaper articles, Martin attacked the proposed new form of government and continued to fight ratification of the Constitution through 1788. He lamented the ascension of the national government over the states and condemned what he saw as unequal representation in Congress. He owned six slaves of his own and opposed including slaves in determining representation and believed that the absence of a jury in the U.S. Supreme Court gravely endangered freedom. At the convention, Martin complained, the aggrandizement of particular states and individuals often had been pursued more avidly than the welfare of the country. The assumption of the term "federal" by those who favored a national government also irritated Martin. Around 1791, however, Martin turned to the Federalist party because of his animosity toward Thomas Jefferson, who in 1807 spoke of him as the Federal Bull-Dog.

The first years of the 1800s saw Martin as defense counsel in two controversial national cases. In the first Martin won an acquittal for his close friend, Supreme Court Justice Samuel Chase, in his impeachment trial in 1805. Two years later Martin was one of Aaron Burr's defense lawyers when Burr stood trial for treason in 1807.

After a record 28 consecutive years as state attorney general, Luther Martin resigned in December 1835. In 2813 Martin became chief judge of the court of oyer and terminer for the City and County of Baltimore. He was reappointed attorney general of Maryland in 1818, and in 1819 he argued Maryland's position in the landmark Supreme Court case McCulloch v. Maryland. The plaintiff, represented by Daniel Webster, William Pinkney and William Wirt, Martin's fortunes declined dramatically in his last years. Heavy drinking, illness, and poverty all took their toll. Paralysis, which had struck in 1819, forced him to retire as Maryland's attorney general in 1822. In 1826, at the age of 78, Luther Martin died in Aaron Burr's home in New York City and was buried in an unmarker grave in St. John's churchyard.