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.