James Hamilton Lewis (May 18, 1863 – April 9, 1939) was an American attorney and politician. Sometimes referred to as J. Ham Lewis or Ham Lewis, he represented Washington in the United States House of Representatives, and Illinois in the United States Senate. He was the first to hold the title of Whip in the United States Senate.

Born in Danville, Virginia and raised in Augusta, Georgia, Lewis attended several colleges, studied law, and attained admission to the bar in 1882. He moved to Washington Territory in 1885, where he became active in politics as a Democrat; he served in the territorial legislature, worked with the federal commission that helped establish the U.S.-Canada boundary, and ran unsuccessfully for governor. He served in the United States House of Representatives from 1897 to 1899.

After service in the Spanish–American War, Lewis relocated to Chicago, Illinois. After serving as the city's corporation counsel, and running unsuccessfully for governor, Lewis won election to the United States Senate in 1912, and served one term (1913-1919). He was chosen to serve as Majority Whip, and was the first person to hold this position. He ran unsuccessfully for reelection in 1918, and for governor in 1920. In 1930, he was again elected to the U.S. Senate, and served from 1931 until his death. He died in Washington, D.C., and was interred first in Arlington, Virginia, and later at Fort Lincoln Cemetery in Brentwood, Maryland.