Colonel William Henry Sykes, FRS (25 January 1790 – 16 June 1872) was an English naturalist who served with the British military in India and was specifically known for his work with the Indian Army as a politician, Indologist and ornithologist. One of the pioneers of the Victorian statistical movement, a founder of the Royal Statistical Society, he conducted surveys and examined the efficiency of army operation. Returning from service in India, he became a director of the East India Company and a member of parliament representing Aberdeen.
Sykes was born near Bradford in Yorkshire. His father Samuel Sykes of Friezing Hall and they belonged to the family of Sykeses of Yorkshire. He joined military service as a cadet in 1803 and obtained a commission on 1 May 1804 with the Honourable East India Company. Joining the Bombay Army he was to lieutenancy on 12 October 1805. He saw action at the siege of Bhurtpur under Lord Lake in 1805. He commanded a regiment at the battles of Kirkee and Poonah and was involved in the capture of hill forts. By 1810 he could speak Hindi and Marathi languages. He became a captain on 25 January 1819 and travelled for four years across Europe from 1820. He returned to India in October 1824 and was appointed by Monstuart Elphinstone as a statistical reporter to the Bombay government. He then collected statistical and natural history researches, and completed a census of the population of the Deccan producing two voluminous statistical reports, and a complete natural history report illustrated with drawings. He married Elizabeth, daughter of William Hay of Renistoun in 1824. He was promoted to the rank of a Major on 8 September 1826 and to Lieutenant-Colonel on 9 April 1831. In December 1829 the post of statistical reporter was abolished but he took leave from military duty and continued to work on his statistical surveys. He completed this in January 1831 and left for Europe on furlough. He retired from active service with the rank of colonel on 18 June 1833 and in September 1835 he became a Royal Commissioner in Lunacy, a post he held till 1845. On account of his knowledge of Indian matters, he was made a director of the East India Company in 1840. In 1867 he was elected chairman of the court of directors of the East India Company.