The album has sold 302,074 copies since its release on Thursday - enough to earn it a platinum award after just three days on sale.
The band have now topped the UK charts with each of their first four studio albums.
Last week's chart-topper, 22 Dreams by Paul Weller, drops to four behind discs by Neil Diamond and Duffy.
Meanwhile, The Fratellis score the second-highest new entry of the week, debuting at five with sophomore effort Here We Stand.
1. (-) Coldplay: 'Viva La Vida'
2. (3) Neil Diamond: 'Home Before Dark'
3. (2) Duffy: 'Rockferry'
4. (1) Paul Weller: '22 Dreams'
5. (-) The Fratellis: 'Here We Stand'
6. (4) Radiohead: 'The Best Of'
7. (7) Neil Diamond: 'The Best Of'
8. (5) Usher: 'Here I Stand'
9. (9) Scooter: 'Jumping All Over The World'
10. (11) Cistercian Monks: 'Chant - Music For Paradise'
> Who's number one on the singles chart? Click here to find out!