Jacob Christian Hansen Ellehammer (June 14 1871 – May 20 1946) was a Danish watchmaker and inventor born in Bakkebølle, Denmark. He is remembered chiefly for his contributions to powered flight.
Following the end of his apprenticeship as a watchmaker he moved to Copenhagen where he worked as an electronics mechanic before establishing his own company in 1898. In the beginning he produced cigarette machines, beverage machines and other electronic machinery. In 1904 he produced his first motorcycle, the Elleham motorcycle.
In 1905, he constructed a monoplane, and in the following year a "semi-biplane". In this latter machine, he made a tethered flight on 12 September 1906, becoming the second European to make a powered flight (after Traian Vuia).
Ellehammer's later inventions included a successful triplane and helicopter.
- The Early Years (Aviation Century), 2003, Ron Dick, Amanda Wright Lane, Dan Patterson, Boston Mills Press, ISBN 1550464078
- Wings: A History of Aviation from Kites to the Space Age, 2004, Tom D. Crouch, W. W. Norton & Company, ISBN 0393326209
- 100 Years of Flight: A Chronology of Aerospace History, 1903-2003 (Library of Flight Series), 2003, Frank H. Winter, F. Robert Van Der Linden, AIAA, ISBN 1563475626