A 16th-Century map that refers to "America" is one of the exhibits
A website offering free access to rare manuscripts, books, films and maps from around the world is being launched by the UN's cultural agency.
Unesco says the World Digital Library will help to promote curiosity and understanding across cultures.
Among the artefacts are a 1,000-year-old Japanese novel and the earliest known map to mention America by name.
About a tenth of the 1,200 exhibits are from Africa - the oldest an 8,000-year-old painting of bleeding antelopes.
But this is an ongoing project in its early stages, and the collection is expected to grow substantially.
The World Digital Library was first mooted in 2005 by James Billington, librarian at the US Library of Congress, the world's biggest library.
The project hopes to expand access to "non-Western" items - though the largest number of items digitised so far are from Europe.
The material is drawn from about 30 libraries and archives across the world, and will be made available in English, Arabic, Chinese, French, Portuguese, Russian and Spanish.
By making cultural treasures accessible to a huge audience, Unesco also hopes to reduce what it sees as a digital divide between rich and poor.
The project is the third such big digitalisation project. Last year the European Union's digital library crashed within hours of its launch, but it is up and running now.