The Unionist Party, later known as the Unconditional Union Party in the border states, was a political party in the United States started after the Compromise of 1850 to define politicians who supported the Compromise. It was used primarily as a label by politicians who did not want to affiliate with the Republicans, or wished to win over anti-secession Democrats. Members included Southern Democrats who were loyal to the Union as well as elements of the old Whig Party and other factions opposed to a separate Southern Confederacy.

The National Union Party was the name used by the Republican Party and elements of other parties for the national ticket in the 1864 presidential election during the Civil War. Most state Republican parties did not change their name. The name was used to attract War Democrats, border state voters, and Unconditional Unionist, and Unionist Party members who might otherwise have not voted for Republicans. The National Union Party nominated incumbent Republican President Abraham Lincoln of Illinois and Democrat Andrew Johnson of Tennessee for Vice President. They won the Electoral College 212–21.