John Gregory (6 September 1806—c. May 1848) was an English railway and naval engineer. He served as engineer aboard HMS Erebus during the 1845 Franklin Expedition, which sought to explore uncharted parts of what is now Nunavut, including the Northwest Passage, and make scientific observations. The ships were outfitted with former railway locomotive engines which served as auxiliary power units, which is why Gregory, who had never been to sea, served on the expedition. All expedition personnel perished in uncertain conditions, mostly on and around King William Island. In 2021, Gregory's remains became the first of the expedition to be identified using DNA analysis.