The boy band's debut album JLS went straight in at number one
Last year's X Factor finalists JLS have seen off Robbie Williams in the race for the top of the album chart.
Williams's much-promoted Reality Killed The Video Star made its album chart debut at number two.
The boy band's debut album, JLS, went straight in at number one despite tough competition from the former Take That star, as well as from Snow Patrol.
The winning margin between the two albums was less than 1%. Both albums sold more than 200,000 copies.
It makes them the biggest selling albums of the year so far.
Unless Williams climbs higher in upcoming weeks, it will be his first studio album not to reach number one.
JLS said: "It is absolutely unbelievable that we have reached the number one spot on the album chart this weekend after such an incredible race with the pop icon that is Robbie Williams!"
Williams, who last week joined his former Take That bandmates on stage at the Children in Need charity concert, has been orchestrating his return to the pop scene for some months.
Black Eyed Peas
Last month he put comeback nerves behind him to perform his first full concert for three years, as part of the BBC Electric Proms in London.
The gig followed an unsteady appearance on X Factor and revelations about him suffering from stage fright.
Reality Killed The Video Star is his first release since 2006's Rudebox, which met with a tepid reception from fans and critics.
Elsewhere in the chart, Up To Now, the best-of album from Snow Patrol, went in at three.
Cheryl Cole's debut album slipped from the top spot to number six.
The Black Eyed Peas were kings of the singles chart this week with Meet Me Halfway, up two this week from number three.
"JLS and Robbie were neck and neck in the end, scoring the two biggest week one totals of the year," said Martin Talbot of the Official Charts Company.
"So while JLS will be rightly delighted with their first number one, Robbie should be too with his biggest opening week sale for four years," he added.