Lionel Simeon Marks (8 September 1871 – 6 January 1955)[1] was a British engineer and one of the pioneers of aeronautics.

During World War II he was a chief consulting engineer to the US Bureau of Aircraft Production.

His Marks' Standard Handbook for Mechanical Engineers is considered as classical reference work.

[5] On 21 June 1906 he married Josephine Preston Peabody, an American poet and dramatist.

[6][7] Marks died of a heart attack in Providence, Rhode Island, aged 83.