James Thompson Farley (August 6, 1829 – January 22, 1886) was an American politician.
He was born in Albemarle County, Virginia, and moved to Missouri and then California at an early age. There he studied law and was admitted to the bar in 1854, commencing practice in Amador County.
He was elected to the California State Assembly from Amador County and served 1855 to 1857, acting as Speaker in 1856. He was a member of the California State Senate from 1869 until 1876, serving as president pro tempore from 1871 to 1872.
He was for several years the recognized leader of the Democratic Party in California, and in 1874 was defeated as a candidate for the U.S. Senate by Governor Newton Booth. He was elected to the Senate from California in 1878 and served from 1879 until 1885. He was not a candidate for renomination in 1884. He resumed the practice of law after leaving Washington, D.C., and died in Jackson, California in 1886. He is buried in City Cemetery in Jackson.