The fourth most watched game was a replay of Japan's incredible upset over South Africa at 6.30pm on Sunday night on Sky Sport 1. This had 2.5 per cent, or over 105,000 viewers.
Other high-viewership games included France v. Italy live on Sky Sport 1 on Sunday morning and a replay of All Blacks v. Argentina on the same channel at 6.30am on Monday morning. Both received over 87,000 viewers.
The figures - sourced from Nielsen TV Audience Measurement (TAM) 19-21 September 2015 AP5+ - are based on a national audience of 4,200,882.
Meanwhile, The Guardian reported that ITV figures in Britain peaked at 9.4 million viewers, with an average of 7.8 million, for England's opening match against Fiji on the weekend.
This makes it the most watched sporting event in Britain this year.
The newspaper reported that more than four in 10 people watching TV at the time were tuned in to the World Cup opener.
SKY Television declined to comment on whether its subscriber numbers had increased due to its broadcasting of the Rugby World Cup.
A SKY spokeswoman also said the company could not share its viewership numbers.