The 1864 National Union National Convention was the United States presidential nominating convention of the National Union Party, which was a name adopted by the main faction of the Republican Party in a coalition with many, if not most, War Democrats after some Republicans and War Democrats nominated John C. Frémont over Lincoln. During the Convention, the party officially called for the end of the ongoing Civil War, the eradication of slavery and the adoption of the Emancipation Proclamation.

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.