The Hawaii-born singer, who debuted on the listings six weeks ago and finished runner-up for the last two, managed to surpass the electro-hop duo's 'Party Rock Anthem' to notch up his third number one.
He previously topped the chart with 'Just The Way You Are' in September 2010 and 'Grenade' this January. His debut LP Doo Wops & Hooligans also debuted at the peak of the album chart the same month.
Elsewhere, US rap star Pitbull joins forces with Ne-Yo, Dutch DJ Afrojack and Nayer to lift 'Give Me Everything' to four from last week's 12, as Lady GaGa's Born This Way promo track 'The Edge Of Glory' arrives at six based on iTunes downloads alone.
The song was named as the 25-year-old's next official single earlier this week following an overwhelmingly positive response from fans, while its predecessor 'Judas' shifts nine places to 11 from last week's 20.
Behind GaGa are a slew of new entries in the shape of Yasmin's 'Finish Line' at 13, Take That's 'Love Love' at 15 and 'Sun Is Up', the latest single from Romanian singer Inna at 17.
Sandwiched between the latter two new arrivals at 16 is Wretch 32 and his Example collaboration 'Unorthodox', down eight places from last Sunday, while Alexandra Stan's 'Mr Saxobeat' climbs an impressive 13 places to land at 18 from its previous finish of 31.
This week's Top 10 in full:
1. (2) Bruno Mars: 'The Lazy Song'
2. (1) LMFAO ft. Lauren Bennet & Goonrock: 'Party Rock Anthem'
3. (3) David Guetta ft. Nicki Minaj & Flo Rida: 'Where Them Girls At?'
4. (12) Pitbull ft. Ne-Yo, Afrojack and Nayer: 'Give Me Everything'
5. (4) Chris Brown ft. Benny Benassi: 'Beautiful People'
6. (-) Lady GaGa: 'The Edge Of Glory'
7. (5) Jennifer Lopez ft. Pitbull: 'On The Floor'
8. (6) Snoop Dogg ft. David Guetta: 'Sweat'
9. (10) Aloe Blacc: 'I Need A Dollar'
10. (9) Jessie J: 'Nobody's Perfect'
Source: Official Charts Company
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