Maguire fired three successive centuries on his way to a 5-3 lead at the Tempodrom and took the first frame of the evening session – but O’Sullivan finished strongest, rattling off five in a row to take control of the 30-year-old Scot.
Prior to this tournament, the penultimate event before the rankings cut-off point to decide which 16 players get automatic places at the World Championship, O’Sullivan was 16th and in danger of missing out on automatic qualification. But this success ensures he will have the chance to win a fourth Crucible crown.
O’Sullivan, who reached this final despite a bout of glandular fever, looked in good touch as he won the opening frame, his break of 111 a taster of the fine fare to come in this best-of-17 contest.
However, Maguire, who whitewashed Shaun Murphy and John Higgins en route to the final, pulled level in the second frame after easing to a confident 130 break, the highest of the tournament.
He followed up with an equally assured 106 in the third and then produced a 128 to move 3-1 ahead after finding himself snookered from the break.
O’Sullivan made a decent start in the first frame after the interval, but when he broke down on 58 Maguire stole in to move 4-1 ahead. A scrappy sixth frame went the way of O’Sullivan before a 55 helped Maguire restore his three-frame lead, but it was the three-time world champion who had the final say at the end of a breathless afternoon’s snooker, a break of 75 giving him renewed hope heading into the evening session.
Maguire won the first frame after the resumption but lost the tenth to a 96 clearance from O’Sullivan, who then picked up the next one to trail by just one. He levelled the match in the 12th frame, punching the air after doing so.
A 67 break after the mid-session interval gave him the lead at 7-6, and soon after it was 8-6, but Maguire held his nerve to stem the tide and stay in the match with a clearance of 82.
It was O’Sullivan, however, who then wrapped up the 16th frame, which lasted nearly 40 minutes, and the match.