James Speed (March 11, 1812–June 25, 1887) was a American lawyer, politician and professor.

He was born in Jefferson County, Kentucky to Judge John Speed and his second wife Lucy Gilmer Fry. He graduated from St. Joseph's College in Kentucky, studied law at Transylvania University and was admitted to the bar at Louisville, in 1833. He joined the Whig Party and became a strong opponent of slavery. In 1847 Speed was elected to the Kentucky House of Representatives, he was a candidate for delegate to Kentucky state constitutional convention in 1849. He agitated for the emancipation of American slaves from an early point in his career. As the American Civil War grew more likely, he worked to keep Kentucky in the Union. He also became a commander of the Louisville Home Guard.

Elected to the Kentucky Senate in 1861 he became the leader of the pro-Union forces in the state during the American Civil War. In 1862 he controversially introduced a bill to "confiscate the property" of those supporting the Confederacy in Kentucky.

In November 1863, President Lincoln appointed him Attorney General of the United States. After the assassination of Lincoln he became associated with the Radical Republican group and advocated the vote for male African Americans. Disillusioned with the increasingly conservative policies of President Andrew Johnson, Speed resigned from the Cabinet in July, 1866 and resumed the practice of his profession.

Speed's radical views were unpopular in Kentucky and his attempt to be elected to the Senate in 1867 ended in failure. In 1868, Speed was a candidate for the Republican nomination for Vice President of the United States.

Speed was a delegate to the Philadelphia "Loyalists' Convention" in 1866 and served as president of the Convention. He was a candidate for U.S. Representative from Kentucky's 5th District in 1870, and was a delegate to Republican National Convention from Kentucky in 1872. He also was a professor in the Law Department of the University of Louisville. He died in Louisville, Kentucky in 1887, and is interred at Cave Hill Cemetery in that city.

He was the father of James Breckinridge Speed and brother of Joshua Fry Speed.