Lucius Israel Barber (October 7, 1806 – February 16, 1889) was an American medical doctor, Whig politician, and Wisconsin pioneer. He served as Speaker of the House of Representatives of the Wisconsin Territory and later served in the Connecticut House of Representatives. In historical documents his name is sometimes incorrectly given as Lucius J. Barber or L. J. Barber. His last name is also sometimes spelled Barbour.