FOURTH-ROUND LEADERBOARD (GB & Ireland unless stated):
-17 S Lowry (am), R Rock -15 J Edfors (Swe) -13 N Dougherty, M Warren -12 A Forsyth Selected others: -9 T Levet -6 D Clarke, O Wilson -5 A Hansen (Den) -3 Pa Lawrie, L Westwood -1 C Montgomerie Par R McIlroy
Shane Lowry celebrates after winning the Irish Open
Shane Lowry became only the third amateur to win a European Tour event by beating Robert Rock at the third play-off hole at the Irish Open at Baltray.
Ireland's Lowry, 22, missed a chance to win in regulation play when he missed a four-foot putt at the 18th.
The pair re-played the 18th and carded pars and then birdies at the second play-off hole before England's Rock bogeyed the hole the third time.
The pair had led into the final day and ended the tournament tied on 17 under.
Lowry and Rock had shared the lead on 16 under after 14 holes, two ahead of Johan Edfors.
Lowry birdied the 16th to lead by one but Rock replied with a birdie on the 17th to draw level again.
The young Irishman drove into the rough at the 18th but then hit a good second shot onto the fairway.
Lowry fired an iron shot to within four feet of the flag but his putt to secure victory slipped tantalisingly left of the hole.
Lowry, Rock and Edfors all ended with rounds of 71 in wet and windy conditions.
The Offaly player joins Danny Lee and Pablo Martin as the only players to win a European Tour event while still an amateur.
Edfors finished third, two behind the leaders, with Nick Dougherty and Marc Warren a further two shots adrift in a tie for fourth.
Alastair Forsyth was sixth on 12 under.
"I thought I had missed my chance when I missed that short putt in normal play - I couldn't believe it," said Lowry.
"Rory (McIlroy) was at the back of the green and he said a few words to me as I left the 18th green.
"He just told me that I was still in it and I had to keep going.
"This is life-changing stuff and I think I will have a busy week ahead."
For Rock, from Armitage in Staffordshire, it was his third second-place finish in as many weeks.
But he had the consolation of amateur Lowry's winner's cheque for 500,000 Euros (just under £500,000) being passed on, earning Rock comfortably the biggest pay day of his career.