Derek Ernest Denny-Brown OBE (1901 – 20 April 1981) was a New Zealand-born neurologist. Working in Oxford, London and Boston, he made major contributions to the field of neurology, such as the development of electromyography, physiology of micturition and the treatment of Wilson's disease.
Born in New Zealand, he studied at the University of Otago at Dunedin, South Island, where he qualified in medicine in 1924. He then took up a fellowship to perform research at the department of Dr Sir Charles Scott Sherrington, where he studied motor neuron physiology. He obtained a DPhil and published sixteen scientific papers on his research.
In 1928 he took up a clinical post at the National Hospital for Neurology and Neurosurgery in London, and over the subsequent years underwent neurological specialist training, as well as serving as a lecturer, at the National Hospital and Guy's Hospital. The National Hospital was at the forefront of the developing specialty of neurology, and he was influenced by some of the senior staff such as Gordon Holmes, Charles Symonds and Samuel Alexander Kinnier Wilson. In 1933 he joined the Territorial Army (TA) section of the Royal Army Medical Corps (RAMC), being commissioned as a lieutenant on 9 December 1933, and promoted captain a year later. He was appointed as a neurologist at St Bartholomew's Hospital in 1935. He spent 1936 in Baltimore at Yale University performing research with former Oxford colleague John Fulton, then returned to London to work at the National Hospital. He married Sylvia Summerhayes in 1937; they were to have four sons. He transferred from the TA active list to the reserve of officers on 5 March 1938.