The Internet.org app is being released first in Zambia, and is to be rolled out in other countries where Internet access is lacking or unaffordable, Facebook said.
"Over 85% of the world's population lives in areas with existing cellular coverage, yet only about 30% of the total population accesses the Internet," Facebook's Guy Rosen said in a blog post.
"Affordability and awareness are significant barriers to Internet adoption for many and today we are introducing the Internet.org app to make the Internet accessible to more people by providing a set of free basic services."
The app allows people with Android-powered mobile phones to get free access to services including Wikipedia, Google Search, Facebook, AccuWeather and websites offering health and other services.
Facebook chief executive Mark Zuckerberg said the app is part of "our effort to bring affordable Internet access to everyone in the world."
"We believe that every person should have access to free basic Internet services -- tools for health, education, jobs and basic communication," Mr Zuckerberg said on his Facebook page.
"Over the past year we've been working with mobile operators around the world to deliver on this goal. We're starting to see this vision become a reality, and we've already helped three million people access the Internet who had no access before."
Mr Zuckerberg said that in Zambia, "only 15% of people in Zambia have access to the Internet," but that "soon, everyone will be able to use the Internet for free to find jobs, get help with reproductive health and other aspects of health, and use tools like Facebook to stay connected with the people they love."
Mr Zuckerberg last year announced the creation of Internet.org to help improve online access around the world, with partners including Ericsson, MediaTek,Nokia, Opera, Qualcomm and Samsung.