Fort Tillinghast was a small lunette that the Union Army constructed in Alexandria County (now Arlington County), Virginia, as part of the Civil War defenses of Washington (see Washington, D.C., in the American Civil War).

[1] Fort Tillinghast stood about 0.6 miles away from Arlington House, the Union-occupied estate of Confederate General Robert E. Lee.

The lunette was named in honor of Captain Otis H. Tillinghast, Quartermaster, killed at the First Battle of Bull Run on July 21, 1861.

[2] In June, 1865, Fort Tillinghast was ordered dismantled and the site returned to its previous owners.

[3] The fortification stood near 205 North Wayne Street in Arlington, but no sections remain today.