Jacob K. Shafer (December 26, 1823 – November 22, 1876) was a Delegate from Idaho Territory. Born near Broadway, Virginia, Shafer was graduated from Washington and Lee University, Lexington, Virginia, in 1843. And from the law school of L.P. Thompson in Staunton, Virginia, in 1846. He moved to Stockton, California in 1849, was admitted to the bar in California and practiced law. He served as district attorney of the fifth judicial district of California in 1850. He served as mayor of Stockton in 1852 and as a judge of the San Joaquin County Court from 1853 to 1862. In 1862 he moved to what later became Idaho Territory.