O'Sullivan, Selby sweep into snooker world semi-finals
Ronnie O'Sullivan after playing a shot against Barry Hawkins during the final match of the World Snooker Championships at The Crucible in Sheffield, England, on May 6, 2013 - by Paul Ellis
Murphy made a strong start to their quarter-final on Tuesday by winning the first two frames, but O'Sullivan roared back and won the next six frames to establish a 6-2 overnight lead.
The five-time champion stretched his advantage to 8-2 on Wednesday morning before 2005 champion Murphy clawed a frame back, but a break of 118 gave O'Sullivan a 9-3 advantage at the mid-session interval.
After a short delay due to a technical problem with the scoreboard, O'Sullivan capitalised on a couple of routine misses by Murphy to close out victory.
O'Sullivan admitted that he had not been expecting such a straightforward victory.
"You just never know what type of match you're going to get," he told BBC television.
"You can expect a really tough match and it turned out easy like it did with Shaun. I didn't expect to win it that easy, to be fair. He's a free-scoring, great potter.
"He just missed a few balls and let me in quite easily. I still had to pot them, but I didn't have to fight for my chances."
Murphy said: "I knew it was going to be a challenge. Nobody has beaten him here for nearly three years and I don't think there's a player in the game he hasn't done that to at some stage."
O'Sullivan will now face either Barry Hawkins or Dominic Dale, with 2013 runner-up Hawkins 11-5 up in their contest at the Crucible Theatre in Sheffield, northern England.
Earlier, Mark Selby finished off a one-sided 13-5 win over Alan McManus to book his place in the last four.
Leading 12-4 overnight, the Leicester cueman needed only one frame to complete victory, but Scottish veteran McManus took the day's first frame thanks to a break of 69.
It proved only a stay of execution, however, and when McManus could not exploit his opportunities in the next frame, Selby pounced to set up a last-four meeting with either Judd Trump or Neil Robertson.
"I think it was four years ago since I was in the semi-final before, so it seems like forever with so many tournaments now during the season," Selby said.
"I'm looking forward to it and can't wait to get out there."
Australian world number one Robertson made a poor start to his last-eight tie against England's Trump and was 6-2 down after the first session on Tuesday.