The track leads the tally for a second week, while Justice Crew leap from seven to two with 'Boom Boom'. Rudimental complete the top three with 'Feel The Love'.
Elsewhere in the top ten, Maroon 5 hold at four with 'One More Night', Justin Bieber and Big Sean vault 34 to eight with 'As Long As You Love Me', and Karmin bound 19 to nine with 'Brokenhearted'.
Further down the chart, Florence + the Machine's 'Spectrum (Say My Name)' lifts from 30 to 14, T-Pain and Ne-Yo's 'Turn All The Lights On' shifts 25 to 18, and Matchbox 20 rise 37 to 28 with 'She's So Mean'.
The Wanted enter at 31 with 'Chasing The Sun', Far*East Movement and Cover Drive's 'Turn Up The Love' debuts at 32, and Ed Sheeran's 'Drunk' is new at 37.
Meanwhile, No Doubt begin at 41 with 'Settle Down', and Chiddy Bang and Icona Pop are at 44 with 'Mind Your Manners'.
The Top 10 singles in full (click where possible for our reviews):
1. (1) fun. 'Some Nights'
2. (7) Justice Crew: 'Boom Boom'
3. (3) Rudimental ft. John Newman: 'Feel The Love'
4. (4) Maroon 5: 'One More Night'
5. (2) Pink: 'Blow Me (One Last Kiss)'
6. (6) Owl City ft. Carly Rae Jepsen: 'Good Time'
7. (5) Katy Perry: 'Wide Awake'
8. (*) Justin Bieber ft. Big Sean: 'As Long As You Love Me'
9. (19) Karmin: 'Brokenhearted'
10. (8) will.i.am ft. Eva Simmons: 'This Is Love'
Watch fun.'s 'Some Nights' music video below: