Around 200,000 oil paintings, representing the entire catalogue of the national collection, are to be made available online.
Works from 3,000 galleries, museums and other public institutions will feature in the Your Paintings project.
From today more than 60,000 paintings by some 15,000 artists will go live online, marking the first phase.
Works from 860 collections feature in the first batch and the entire archive is expected to be completed by the end of next year.
A number of artists and celebrities have also highlighted their favourites, including names as diverse as comic Frank Skinner, One Show host Matt Baker, Gardener's World presenter Monty Don and Turner Prize nominee Yinka Shonibare.
Works held by the likes of the National Trust and displayed in hospitals or fire stations also feature.
The project is a collaboration between the Public Catalogue Foundation (PCF) and the BBC and can be seen at bbc.co.uk/yourpaintings.
Members of the public will be asked to "tag" the paintings with key words to make it easier to search for subjects over the coming months.
The BBC will also broadcast a number of programmes to support Your Paintings.
Nicholas Penny, director of the National Gallery, said: "Thanks to the initiative of the PCF and the BBC, the concept of a national collection has suddenly altered.
"They have extended, in an exciting way, our understanding of what are in 'public ownership' is, and our access to it."
Roly Keating, the BBC's director of archive content, said: "Your Paintings will be a hugely valuable learning resource for our audience and demonstrates the power of working with partners to open up the nation's cultural resources."