The Constitutional Union Party was a political party in the United States created in 1860. It was made up of conservative Whigs who wanted to avoid disunion over the slavery issue. These former Whigs teamed up with former Know-Nothings to form the Constitutional Union Party. Its name comes from its extremely simple platform, a simple resolution "to recognize no political principle other than the Constitution...the Union...and the Enforcement of the Laws." They hoped that by failing to take a firm stand either for or against slavery or its extension, the issue could be pushed aside.

In short, it was a place to go for Whigs and Know-Nothings unwilling to join Democrats or the Republicans. Senator John J. Crittenden of Kentucky, Henry Clay's successor in border-state Whiggery, set up a meeting among fifty conservative, pro-compromise congressmen in December 1859, which led to a convention in Baltimore the week of May 9, 1860, one week before the Republican Party convention.

The convention nominated John Bell of Tennessee for President and Edward Everett of Massachusetts for Vice President.

In the 1860 election, the Constitutional Unionists received nearly all of their votes from former southern Whigs, and managed to win three states (Virginia, Kentucky, and Tennessee), although this was largely due to the split in Democratic votes between Stephen A. Douglas and John C. Breckinridge.

Bell and many other Constitutional Unionists later supported the South during the Civil War, and the party and its purpose disappeared after 1860.