Rosberg got the jump on polesitter Hamilton into Turn 1, but his team mate got a much better run out of Turn 3. As the world champion went for the inside line into Turn 4, he ran out of room as Rosberg defended and got a wheel on the grass.
Hamilton was pitched into a spin and collected Rosberg in the process, sending both men into the gravel where they found themselves beached and out of the race.
Stewards will investigate the incident after the race, which brought out the safety car and left the Red Bulls of Daniel Ricciardo and Max Verstappen leading from Toro Rosso’s Carlos Sainz and Ferrari’s Sebastian Vettel.
It means Mercedes record their first double retirement since Australia 2011, and fail to score for the first time since Brazil 2012.
For live commentary from the race, click here.
WATCH: Rosberg and Hamilton collide in Spain
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