The team-mates were separated by two tenths of a second, but were over two seconds clear of the chasing pack. Sebastian Vettel put in a strong performance to complete the top three, ahead of Fernando Alonso.
The session began in extremely treacherous conditions, though the track slowly dried throughout proceedings. The rain did not produce a topsy-turvy grid, but another star performance from Jules Bianchi put him in Q2 for the second successive weekend. There was less joy for Pastor Maldonado, who had a spin on his way to 17th and elimination, and Nico Hulkenberg, who was a shock 18th. Max Chilton took 19th while Esteban Gutierrez was sidelined by technical issues, leaving him 20th.
At the very bottom of the timesheet Caterham newcomer Andre Lotterer beat team-mate Marcus Ericsson by a full second, ensuring an excellent start to his surprise F1 debut.
Q2 produced no notable eliminations. Toro Rosso team-mates Daniil Kvyat and Jean-Eric Vergne will start 11th and 12th respectively, followed by Sergio Perez, Adrian Sutil and Romain Grosjean. Bianchi was the slowest man in Q2, leaving him 16th for tomorrow's race.
The top-10 shootout seemed to be headed Rosberg's way from the start. The German put in a strong opening run while Hamilton made a mistake early on his first flying lap, allowing Nico to steal a march of almost seven tenths.
Hamilton battled back, but had a similarly scruffy start to his second lap. Although he subsequently pulled time back, the Brit eventually fell a tenth short of his team-mate. Rosberg then went quicker still to ensure his pole in style.
Vettel and Alonso were next up, two seconds down on the Mercedes cars, followed by Daniel Ricciardo and Valtteri Bottas. Kevin Magnussen will start seventh after comfortably outperforming team-mate Jenson Button, who ended the session in P10. Between them on the grid will be Kimi Raikkonen and Felipe Massa.
Belgian Grand Prix - Qualifying Top 10
- Nico Rosberg (Mercedes)
- Lewis Hamilton (Mercedes)
- Sebastian Vettel (Red Bull-Renault)
- Fernando Alonso (Ferrari)
- Daniel Ricciardo (Red Bull-Renault)
- Valtteri Bottas (Williams-Mercedes)
- Kevin Magnussen (McLaren-Mercedes)
- Kimi Raikkonen (Ferrari)
- Felipe Massa (Williams-Mercedes)
- Jenson Button (McLaren-Mercedes)