Harold Arthur Lee-Dillon, 17th Viscount Dillon, CH, FBA, FSA (24 January 1844 – 18 December 1932) was an English antiquary and a leading authority on the history of arms and armour and medieval costume.

The eldest son of Arthur Dillon, 16th Viscount Dillon, he was born in Victoria Square, Westminster, and educated at private school and at the University of Bonn, Germany.

After leaving the regular army he devoted himself to antiquarian study, writing over fifty books and articles.

[6] He bequeathed to the trustees various portraits from Ditchley Park, Charlbury including the portrait of his ancestor Sir Henry Lee by Antonio Moro.

He was the founding president of the Society for Army Historical Research holding the position until his death.