Lovell Harrison Rousseau (August 4, 1818 – January 7, 1869) was a general in the Union Army during the American Civil War, as well as a lawyer and politician in Kentucky and Indiana.

Rousseau was a member of the Whig Party early in his political career and later became a member of the Unconditional Union Party. He was a member of the Indiana State Senate from 1847 to 1849 and was a member of the Kentucky State Senate from 1860 to 1861. During the Civil War, Rousseau served in the Union Army as a colonel, a brigadier general, and a major general. He served in the Thirty-ninth Congress, resigned, and was re-elected to Congress. Rousseau was censured by the House of Representatives in 1866 for assaulting Rep. Josiah B. Grinnell on the House floor.

Rousseau was made a brigadier general in the U.S. Army in 1867 and given the brevet rank of major general. Thereafter, he served in Alaska and Louisiana.

Born near Stanford, Kentucky, on August 4, 1818, Rousseau attended the common schools as a child. His father, David Rousseau, brought his family across the Appalachians from Virginia, but he had a difficult time regaining economic equilibrium (despite extensive holdings in undeveloped land and slaves). Lovell's elder brother had already left home, so when their father died of cholera attempting to move the family to a new home in 1833, it fell to Lovell and his younger brothers to dig their father's roadside grave. At age fifteen, he had become his family's primary breadwinner. Soon afterwards, he was forced to sell his family's slaves in an effort to cover the family's debts.

Eager to earn a wage, he began working on a road-building crew, traveling around the Midwest. Determined to rise, he studied grammar, mathematics, and French, and returned to Kentucky where he read law in Louisville, Kentucky, for several months. In 1841, he passed the Indiana bar examination and began practicing law with his brother, Richard Hillaire Rousseau, as junior partners in a firm led by James I. Dozier, in Bloomfield, Indiana. Both brothers married Dozier's daughters. Richard married Mary E. Dozier in 1839, while Lovell married Maria A. Dozier in 1843. (Mary Dozier Rousseau died young, and Richard remarried.)

Lovell successfully ran for the Indiana House of Representatives as a Whig candidate in 1844, and in 1846 he was commissioned as a captain in the Mexican–American War and charged with raising a company of volunteers. He led them at the Battle of Buena Vista, where he helped rally the Indiana troops at a key point in the battle.

When he returned from the war, he gained a seat in the Indiana Senate and continued to run a successful law practice.

After relocating to Louisville, Kentucky, he served in the Kentucky Senate from 1860 to 1861.