Online subscription will cost £2 per week.
Readers of The Sun must now pay to visit its website after it introduced a paywall.
The online version of the paper, called Sun+, costs £2 per week to subscribe to, compared to its print edition, which costs £3.20 a week.
Online readers can read 20 stories free per month before having to pay for access, similar to the policy adopted by the DailyTelegraph in March.
The Times went behind a paywall three years ago and the Financial Times also charges for access.
The Sun, owned by Rupert Murdoch, has a 2.3m print circulation, while about 1.7m visit the website a day.
Sun+ will try and encourage people to sign up with offers including access to videos of all Premier League goals.