It is a 41st career ranking title for the world number one and his third World Grand Prix.
Trump (#2) got off to a flying start, taking a 4-0 lead before O'Sullivan pulled it back to 5-3 at the break.
'The Rocket' went 6-3 down in the evening session, but a stunning comeback saw him claim the crown.
Speaking afterward, O'Sullivan told ITV: "Judd blasted off the table to go 4-0 up and I thought this could be an early night.
"I managed to nick a few frames this afternoon and at 5-3 it gave me a bit of optimism.
"You have to battle against Judd because he is a warrior. For me, he is the favourite for the World Championship this year."
