Kilmarnock trio Simon Neil and twins Ben and James Johnston reached No. 2 and No. 3 respectively with their two previous studio albums, 2007s Puzzle and 2009s Only Revolutions.
They told the Official Charts Company: "Opposites feels like the best record we've ever made and to have it sitting atop the Official Albums Chart is a huge honour."
The double album has sold an impressive 71,500 copies this week, which is not only the biggest opening week tally for an album this year so far, but also a personal best for Biffy, eclipsing the first week sales of their previous Top 10 albums (Puzzle 37,000 and Only Revolutions 43,000 ).
Opposites relegates The Motion Picture Cast Recording of Les Miserables to No. 2 on the chart while, 35 years after its release, the the seminal Fleetwood Mac album Rumours is back in the Top 3.
Scot Emeli Sande is at No. 4 with Our Version Of Events, while the acoustic revamp of Justin Bieber’s Believe completes this week’s Official Albums Chart Top 5.
There are two other new releases in the top 10: Italian tenor Andrea Bocelli is at No. 9 with his 14th studio album Passione, whilst Conduit, the sixth album by Welsh rockers Funeral For A Friend, finishes the week at No. 34.