The ITV show had an average audience of 8.4 million, including those watching on the catch-up +1 channel, which was down 100,000 on the Saturday stage of last year’s final.
The only time it has fared worse was in 2004, when it pulled in 8.1 million for the first-ever final, won by Steve Brookstein.
Strictly – which has been ahead throughout this series and last night reached its semi-final stage – drew 9.9 million, also down 100,000 on the equivalent show last year.
The X Factor has seen a marked decline in its audience over recent years. In 2010 – when Matt Cardle was the winner – the equivalent show drew 14.1 million viewers.
X Factor viewers will tonight see the winner crowned in the second stage of the final, with van driver Ben Haenow competing against hot favourite Fleur East.
It is not yet known if she will be well enough to come back for tonight’s programme.