James Beauchamp Clark (March 7, 1850 – March 2, 1921) was an American politician and attorney who served as the 36th speaker of the United States House of Representatives from 1911 to 1919. He was the only Democrat to serve as speaker during the Progressive Era when Republicans dominated the House, Senate, and presidency. Clark represented Missouri's 9th district between 1893 and 1921.

Born in Kentucky, Clark established a law practice in Bowling Green, Missouri. After serving in local, county, and state office, he won election to the U.S. House in 1892, lost his seat in 1894, and won the seat back in 1896. He became the House Minority Leader in 1908 and was elevated to Speaker after Democrats took control of the House in the 1910 elections. He inadvertently helped defeat the Canadian–American Reciprocity Treaty of 1911 by arguing that ratification of the treaty would lead to the incorporation of Canada into the United States.

Entering the 1912 Democratic National Convention, Clark had won the backing of a majority of the delegates, but lacked the necessary two-thirds majority to win the presidential nomination. After dozens of ballots, Woodrow Wilson emerged as the Democratic presidential nominee, and went on to win the 1912 presidential election. Clark helped Wilson pass much of his progressive agenda but opposed U.S. entry into World War I. In the 1918 midterm elections, Democrats lost their control of the House of Representatives, ending Clark's tenure as Speaker. The 1920 House elections saw the defeat of numerous Democrats, including Clark. He died the following March, two days before he would have left office.