Horace Holmes Thomas (December 18, 1831 – March 17, 1904) was a lawyer, Union Army officer, state legislator, and appraiser in Illinois who served in the Illinois House of Representatives and Illinois Senate. He was a Speaker of the Illinois House of Representatives from 1880 to 1881. He was born in Hubbardton, Vermont, graduated from Middlebury College, and studied law. He moved to Chicago in 1859.