The companies will first offer the app in seven of India's 22 regions, or zones and it will then go nationwide in the next 90 days, Gurdeep Singh, chief executive of Reliance's consumer business told reporters.
The service is run by Internet.org, the non-profit organisation whose backers also include Ericsson , Nokia, Samsung, Qualcomm and Opera Software, which has the declared aim of making basic Internet services available to the two-thirds of the world's population which is not yet connected.
The app, aimed at low income and rural users, will offer free access via mobile phone to more than 30 pared-down web services, focused on job listings, agricultural information, healthcare and education sites in seven regional languages -- as well as Facebook's own social network and messaging services.
It will be available to all of Reliance's 106.3 million subscribers who have handsets capable of handling internet traffic.
Singh declined to comment on who will bear the cost of carrying this data traffic for free.
Mobile phones sales have been booming in India, the world's second-biggest mobile market, with smartphone sales surging 90% in the October-December quarter. But less than 20% of the country's population can access the Internet -- leaving over a billion people offline.
Facebook said it had worked with Reliance Communications since last October to address barriers to connectivity.
Both Reliance and Facebook said they also expected to benefit from the venture over the longer term. India has the world's third-largest population of Internet users, and could take the number two spot this year.
"It gives us a great lever in terms of our proposition differentiation at the point of sale ... which will help us accelerate our acquisition journey of good quality, sticky customers," Singh said.
Singh said the company has beefed up infrastructure to meet the anticipated increase in data traffic, but did not give details on the amount it had spent.
"We address the affordability of data by having beneficial services and then we'll make it scalable for our partners so that once these users want to use more, they just buy the regular (data) plan," Markku Makelainen, Facebook's director of Global Operator Partnerships, told Reuters.
"One of our goals is to have a profitable partnership."
Facebook has partnered with more than 150 wireless providers over the past four years to offer free or discounted access to its social network, but the new Internet.org app is the first time the company has added services beyond its own website.
The service comes to India following similar launches in Zambia, Tanzania, Kenya, Ghana and Colombia.