Henry Moore Harrington (April 30, 1849 – June 25, 1876) was a military officer in the 7th United States Cavalry Regiment who went missing in action during the Battle of Little Big Horn in Montana Territory.

In the summer of 1874, Harrington and his Company C were part of the 7th Cavalry's military escort for the Black Hills Expedition under the command of Lieutenant Colonel George Armstrong Custer.

On May 17, 1876, during the Great Sioux War of 1876, Brigadier General Alfred Terry's Dakota column departed Fort Abraham Lincoln and embarked on the Little Big Horn campaign.

After Harrington and the over 300 soldiers on the Reno Scout rejoined Colonel Custer and the 7th Cavalry, the regiment marched up Rosebud Creek, then crossed to the Little Bighorn River.

On June 25, 1876 the 647 men with the 7th Cavalry including Henry Harrington under the command of George A. Custer attacked a village of several thousand Native Americans, in what became known as the Battle of the Little Bighorn.