The National Union Party, commonly the Union Party or Unionists, was a wartime coalition of Republicans, War Democrats, and border state Unconditional Unionists that supported the Lincoln Administration during the American Civil War. It held the 1864 National Union Convention that nominated Abraham Lincoln for president and Andrew Johnson for vice president in the 1864 United States presidential election. The National Union Convention was organized just before the general election of November 1864, when the Civil War was still in progress.

Following Lincoln's successful re-election and assassination, Johnson tried and failed to sustain the Union Party as a vehicle for his presidential ambitions. The coalition did not contest the 1868 elections, but the Republican Party continued to use the "Union Republican" label throughout the period of Reconstruction. Besides allowing voters of diverse pre-war partisan allegiances to unite under a common banner, the Union label served a valuable propaganda purpose by implying the coalition's opponents were dis-unionists.