Elisabeth (Elly) Dekker (Haarlem, 1943) is a Dutch astronomer and science historian, specialising in the history of astronomy. She studied theoretical physics and astronomy at Utrecht University. In 1975 she obtained a PhD in astronomy at Leiden University with the thesis Spiral structure and the dynamics of flat stellar systems supervised by Hendrik C. van de Hulst. From 1978-1988 she was a curator of Museum Boerhaave in Leiden and afterwards an independent scholar. From 1993-1995 she was a Sackler fellow of the Royal Museums Greenwich. In 1998 she was awarded the Caird Medal for her work on the globe collection of the National Maritime Museum in Greenwich.