Lieutenant Harley de Lange was a Starfleet security officer who served during the late 24th century.

Before serving on the Enterprise, he had a tour of duty on Starbase 23. After joining the ship, he enrolled in Zelik Leybenzon's martial arts class, and attained a green belt. He had a delusion about the planet Dorcas. (TNG novel: Q & A)

By 2381, he had attained the rank of Lieutenant aboard the Enterprise. During the Borg Invasion of 2381, the USS Aventine and the Enterprise traveled through a subspace tunnel from the Azure Nebula, hoping to find the staging area of the Borg, but ended up near the Carina Arm near the border of the Delta and Gamma Quadrants. A fleet of Hirogen vessels attacked and boarded the two vessels, and de Lange was part of Randolph Giudice's security team to defend the vessel, all armed with TR-116 rifles. As the Hirogen hunters approached, their energy dampeners knocked out the lighting, and de Lange and Manfred Vogel were impaled with starburst-shaped throwing blades, dead before their bodies struck the deck. (ST - Destiny novel: Mere Mortals)

USS Enterprise (NCC-1701-E) security & tactical personnel
	Chiefs: L. Addison • P. Daniels • Rowan • R. McAdams • B. Leyoro • C. Vale • S. Nave • L. Battaglia • Z. Leybenzon • J. Choudhury
	Aiken • J. Allen • Almonte • A. Balidemaj • A. Braddock • Brennan • G. Carmona • Carr • A. Chang • Chell • N. th'Chun • Clemens • Cobbins • Craycroft • K. Cruzen • P. Davila • H. de Lange • Dey • R. Duncan • S. Fillion • Floyd • R. Giudice • J. Gonzales • T. Gracin • E. Grigsby • Jarata B. • Korban • J. Jurot • Kelly • ch'Kerrosoth • E. Laird • Lightner • Le Roy • J. Lofgrin • Lopex • Liryn • F. McEwan • R. Mars • Melo • A. Munro • T. Murphy • Obarakeh • Parminder • J. Peart • Razka • B. Regnis • Sanders • N. Sirhc • A. Šmrhová • S. Stockman • N. Stolovitsky • J. Struhlem • K. Thompson • J. Travis • T'Sona • M. Vogel • F. Wriede
see also: Senior staff • Engineering • Flight Control • Medical and Counseling • Operations • Science • Security • Misc. • Unnamed