Born at West Harling Hall, Norfolk, England. Ridley was the first Scientific Director of the Singapore Botanic Gardens from 1888 to 1911.
Ridley spent many years promoting rubber as a commercial product, which he was known for being passionate; therefore, he was nicknamed "Mad Ridley". In 1895, he discovered a means of tapping which did not seriously damage the rubber trees. Ridley was also largely responsible for establishing the rubber industry on the Malay peninsula, where he resided for twenty years before publishing, in 1930, a seminal and comprehensive work on plant dispersal. This work was the culmination of his own observations over several years, and a review of widely scattered literature on the subject.
Ridley retired from Singapore in 1911 and resided in England for the remainder of his life. On his 100th birthday in 1955 he received a visit from the High Commissioner of the soon-to-be independent Malaya.