The track notches up a second week at the summit, while Psy's 'Gangnam Style' holds at number two.
Meanwhile, Ke$ha's 'Die Young' jumps six to three, Macklemore & Ryan Lewis leap 19 to four with 'Thrift Shop', and One Direction are new at nine with 'Little Things'.
Outside the top ten, X Factor Australia's Samantha Jade lands at 12 with 'Heartless', David Guetta and Sia's 'She Wolf' rebounds 31 to 18, and Guy Sebastian's 'Get Along' is new at 34.
Flight Facilities start at 38 with 'Clair de Lune', Adele's 'Skyfall' re-enters at 41, and X Factor's The Collective start at 47 with 'Apologise'.
The top ten singles appear below (click where possible for our reviews):
1. (1) Swedish House Mafia: 'Don't You Worry Child'
2. (2) Psy: 'Gangnam Style'
3. (6) Ke$ha: 'Die Young'
4. (19) Macklemore & Ryan Lewis: 'Thrift Shop'
5. (4) Bruno Mars: 'Locked out of Heaven'
6. (7) Sam And The Womp: 'Bom Bom'
7. (5) Calvin Harris ft. Florence Welch: 'Sweet Nothing'
8. (9) Taylor Swift: 'I Knew You Were Trouble'
9. (*) One Direction: 'Little Things'
10. (8) Rihanna: 'Diamonds'
Watch Swedish House Mafia's 'Don't You Worry Child' video below: