William Linn McMillen (October 18, 1829 – February 8, 1902) was an American surgeon, army officer, farmer and carpetbagger legislator.

McMillen served as a surgeon with the Russian Army in the Crimean War, returning to Ohio in 1856.

[1] Accused of cowardly conduct during that engagement (in which he and about half the Union forces involved were captured), he was court-martialed, tried and acquitted after his release.

[3] In Smith's obituary, it was stated that when McMillen's role in Smith's injuries became public knowledge, McMillen was asked to relinquish his office in the New Orleans chapter of the Grand Army of the Republic.

[4] On December 12, 1864, President Abraham Lincoln nominated McMillen for appointment to the grade of brevet brigadier general of volunteers, to rank from December 16, 1864, and the United States Senate confirmed the appointment on February 14, 1865.