Robertson appeared to be cruising to victory but Ding showed resilience and pure break-building class in winning the last four frames of a memorable final. Victory gave the 25-year-old from China the sixth ranking title of his career and first since the Welsh Open 13 months ago, not to mention the £100,000 top prize.
This season's PTC series has covered 14 tournaments across the globe, and Ding ended up the last man standing after a thrilling final enjoyed by a packed crowd in the west of Ireland on St Patrick's night.
A snooker genius who won three ranking titles before his 20th birthday, Ding's biggest weakness in recent years has been a tendency to lack fighting spirit when behind in matches. He could certainly not be accused of that this week as he trailed Andrew Higginson 3-1 and Robertson 3-0 but came back to win 4-3, as well as claiming two other matches in deciding frames.
Ding's exceptional scoring capacity was also on full display as he made eight centuries in his five matches, including a brilliant 147 maximum against Mark Allen yesterday. In this form he will be one of the leading contenders for the World Championship, which starts in five weeks.
Australia's Robertson missed out on his seventh ranking title and lost in the final in Galway for the second consecutive year. It was a fourth consecutive defeat in major finals for the 31-year-old as he also lost to Judd Trump at the International Championship and to Mark Selby at the Masters. He banks £40,000 but is without a ranking title since the 2010 World Open.
Ding had the first chance in the opening frame and made 41 before running out of position. Robertson stepped in with a superb 88 clearance, including a clever shot to move the last red away from a side cushion. The Aussie dominated the next frame with a top break of 58 for 2-0.
In frame three, Robertson missed a mid-range red to a top corner, and Ding made 51 before missing a red with the rest. Again Robertson took full advantage with a smooth 60 clearance, making easy work of the green which was close to a baulk cushion.
Ding started the next with a run of 52 before missing a tough red to a centre pocket. Robertson attempted a long red to a baulk corner but missed his target and Ding added 70 to avoid the possibility of a white-wash. And his fight-back gathered pace with a stunning 130 total clearance for 3-2.
In frame six, Robertson had a match-winning chance but ran out of position on 44. Ding built a six-point lead before over-screwing from black to yellow. After a safety exchange, Ding cleared from yellow to pink, rolling a brave brown along the baulk cushion which could have cost him the match.
Robertson missed a long red early in the decider and Ding knocked a cracking pot into a baulk corner. After opening the pack off the blue he never looked like missing and made a cool 98 to finish in style.
"I have played well all week. It was very tough because I had to win four matches in the last frame," said Ding, who is the ninth different winner in nine ranking events this season. "I have taken my chances, made big breaks and fought back in matches.
"I have more experience now and I know I can win close matches with just one chance. It's all about thinking, and keeping my concentration. I have been working hard all year. I might have a few tournaments when I don't play well and have less energy, but I know I can come back strong."
Asked if he feels he has his best chance yet to win the World Championship, Ding added: "I feel confident, I think I can win more titles if I can keep this form. I will keep practising. I am enjoying matches now and making big breaks."
Robertson said: "I didn't get a clear chance to win it. I've lost four big finals in a row but all of them have been against players at the top of their game. The way Ding played tonight from 3-0 down was as good as Ronnie O'Sullivan. I didn't miss anything in the first three frames and then I was just waiting for a chance but I was a bit unlucky a couple of times.
"I'm really disappointed to lose because I don't want to make a habit of losing finals, although it's not as if I'm throwing them away. The standard in the final was fantastic and there wasn't much I could do in the end."
Ball by ball scoring and results from tournaments