Some 20,000 items contained in around 90,000 images were published on the Internet, according to a spokesman for Cambridge University, the scholar’s old academic home.
Chief among them was the first draft of Darwin’s "The Origin of Species", produced in the 1840s, which eventually led to the publication of his most well-known work in 1859.
"This release makes his private papers, mountains of notes, experiments and research behind his world-changing publications available to the world for free," said John van Wyhe, the director of The Complete Work of Charles Darwin Online project.
"The release of his papers online marks a revolution in the public’s access to - and hopefully appreciation of - one of the most important collections of primary materials in the history of science," he added, describing the collection as a "treasure trove".
Along with "The Origin of Species" and other scientific papers, the collection includes photographs of him and his family, reviews of his books, newspaper clippings, as well as material revealing his home life, notably a recipe for boiling rice, inscribed in Darwin’s own handwriting.
Among the scientific papers available are notes from his famous voyage on the HMS Beagle, a five-year journey which started in 1831 and took Darwin to South America and Australia, where he collected huge numbers of samples of fossils and living organisms.
It provided the basis for much of his future work and brought him success and celebrity on his return to Britain.
Darwin produced evidence to show that mankind originated through evolutionary change effected by natural selection and his findings are now considered central to our understanding of biology.
The collection can be found at http://darwin-online.org.uk/.