The Times and Sunday Times newspapers will start charging to access their websites in June, owner News International (NI) has announced.
Users will pay £1 for a day's access and £2 for a week's subscription.
The move opens a new front in the battle for readership and will be watched closely by the industry.
NI chief executive Rebekah Brooks said it was "a crucial step towards making the business of news an economically exciting proposition".
Both titles will launch new websites in early May, separating their digital presence for the first time and replacing the existing, combined site, Times Online.
The two new sites will be available for a free trial period to registered customers. And payment will give customers access to both sites.
With newspaper sales in decline, companies have been searching for a business model that will make money from their websites.
But with so much news content available for free on the internet, NI's decision to charge is seen by many people as a high risk strategy.
Rupert Murdoch, whose News Corp owns NI, has led a fierce campaign against internet sites which distribute news content from his companies. He has criticised Google in particular.
James Harding, editor of The Times, agreed that NI's paywall strategy was a risk. "But it's less of a risk than just throwing away our journalism and giving it away from free," he told the BBC.
He likened the news industry to the music industry of four years ago. "People said the game is up for the music industry because everyone is downloading for free. But now people are buying from download sites."
Mrs Brooks said the decision to charge came "at a defining moment for journalism... We are proud of our journalism and unashamed to say that we believe it has value".
Just the start
And she hinted that two other News International publications, The Sun and the News of the World, would also go behind a paywall.
"This is just the start. The Times and The Sunday Times are the first of our four titles in the UK to move to this new approach. We will continue to develop our digital products and to invest and innovate for our customers."
Privately, executives admit the two papers are likely to lose thousands of regular online readers - and millions of more casual ones - says BBC media correspondent Torin Douglas. But they hope £2 a week is a small enough sum to entice many readers over the paywall.
We can expect marketing campaigns to make comparisons with the price of a cup of coffee, "by which standard, newspapers remain astonishingly good value," our correspondent says.
The media industry uses a general yardstick that about 5% of visitors to news websites are likely to pay for content. Latest figures show that The Times and Sunday Times had 1.22m daily users.
However, Claire Enders, of media research company Enders Analysis, says that anyone who believes the Times papers will get a 5% conversion is in "dreamland".
"This is not just about adding subscribers, but also strengthening the relationship with loyal readers of the website and papers. If you are going to try this [charging] then the model they have chosen is the best way," she said.
News Corp owns the Wall Street Journal, which has one of the most successful paid-for sites with about 407,000 electronic subscribers.
But some analysts point out that the WSJ offers specialist content, and that charging for general news is a different business model.
The editor-in-chief of the Guardian, Alan Rusbridger, is a leading sceptic of paywalls and has vowed to keep most of the content of his newspaper free online. In January he described the move towards paywall business models as a "hunch".
Unlike some commentators, Ms Enders does not expect any of the major UK newspaper groups to follow suit quickly.
Nor does she believe that Mr Murdoch's strategy represents the last throw of the dice for some of his loss-making papers. "If it fails, Murdoch will think of something else. He has been supporting his loss-makers for years."