Kurten rode Lady Georgina Forbes's mare Castle Forbes Libertina to victory in the prestigious event and collected a cheque for e42,000.
Nine riders from the 39 starters returned for a jump-off, where Kurten out shone the opposition with a stunning double clear to take first place.
The Co Antrim born rider's flawless second round was enough to see off the challenge from Belgian rider, Patrick Spits, who had to settle for second place after recording a single time fault.
Speaking after the event, Kurten said: "I have dreamt of this ever since I was a kid. I felt the crowd was behind me."
The top two in the Grand Prix were also amongst the prizes in The Longines Leading International Rider and Leading Irish Rider Awards. Patrick Spits won leading international rider award and Jessica Kurten won the leading Irish rider award.
A promising bid for the trophy by 37 year-old Irish rider Niall Talbot and Tequi D'I CH, who recorded the only other zero score in the penultimate round, came adrift when the combination left one pole on the ground to take fifth place overall.
Germany's Alois Pollman Schweckhorst on Lord Luis and Egypt's Abdel Said on Team Harmony Sky High completed the top five.
Mayo-born Cameron Hanley finished in 11th place on Southwind VDL, while Capt. David O'Brien was 14th on the grey Cruising mare Mo Chroi.