John Williams Reynolds (25 December 1816 – 28 July 1874) was an English cavalry officer and organic chemist. His disagreement in 1840 with Lord Cardigan, his commanding officer, (the notorious "black bottle affair") made him famous, and a popular cause célèbre in London. At the end of 1840, he left his regiment to study at the Royal Military College, Sandhurst. After graduating, he did not return to regimental duties but took up the study of organic chemistry at the Royal College of Chemistry, London. He discovered the compound propylene, thus advancing the theory of homology. He was recalled to service in 1851 and rose to the rank of Major-General.
