The two organisations have agreed to digitise the university library's out-of-copyright books, placing some of the greatest works of Spanish literature on the web.
As well as its collection of Spanish-language public domain books, the university will also make available works of Spanish historic importance, as well numerous books in French, German, Latin, Italian and English.
"Out-of-copyright books which were previously available only to people with access to Madrid's Complutense University library, or the money to travel, will now be accessible to everyone with an internet connection wherever they live," said Carlos Berzosa, chancellor of the Complutense University.
"We are quite literally opening our library to the world, and the opportunities for education are phenomenal."
Complutense University is the first Spanish partner to join Google's Library Project.
"More than 400 million people speak Spanish worldwide and this literature holds important cultural significance, so we are enormously excited about working with the Complutense University," said Susan Wojcicki, vice president of product management at Google.
Incisive Media and Investec Asset Management supported fundraiser crosses Atlantic in 40 days
Alphabet's health sciences division Verily have been messing with AI algorithms
North Korea's cyber attack capabilities are expanding fast - and turning their fire on a wider range of targets
IT security? We've heard of it, claim UK local authorities