The five-time world champion started the week in Preston on 994 career centuries and looked set to become the first player to reach the 1,000 mark when he rolled in a 101 break in the opening frame of his first round win over Barry Hawkins.
Number 996 and 997 soon followed during his 6-4 quarter-final triumph over John Higgins, but could not add to his total in his 6-0 whitewash of Mark Allen in the last four.
— World Snooker (@WorldSnooker) March 10, 2019
O'Sullivan looked set to be stranded on 999 after two centuries in the afternoon session, while a 9-4 lead at the mid-session interval in the evening let him within one frame of his 35th career ranking title.
But he defended his title in style, teasing the fans by stopping his approach while on 99 before potting the red left-handed and recording a 134 break, where he even managed to pot the white after sinking the final black to deny a superb 141 finish.
After creating his latest piece of snooker history, O'Sullivan told ITV4: "I just played really, really well.
"I played well all week, but I played brilliantly today and to cap it off with 1,000 centuries is great.
"I suppose to me, it's just what I do since I was seven or eight, playing snooker, potting balls – I love the game. But to share it with the fans in Preston and any snooker fans, Preston are just lucky that it was here tonight.
"This should be the base for what venues should be because you will get better matches. Players love playing here. It's one of the best venues and it's great.
"When you put top-quality players in top-quality venues then you will get top-quality snooker and that is what the Guild Hall is.
"To me, snooker is just a sport, it's a game and everyone here loves to watch the game. But as far as human beings go, he's (Robertson) one of the nicest human beings on the circuit so for me that means more.
"It was nice that I have done it with an opponent I have a lot of respect for."
O'Sullivan's attempt at snooker history was not the only talking point of the week as the 43-year-old maverick has bizarrely adopted an Australian accent in post-match interviews, and also claimed to have set up an all-Australian final against Robertson.
In Sunday's finale, 'The Rocket' rattled in a 67 break during the opening frame before there was controversy in the next as he complained to referee Terry Camilleri over the re-spotting of the black.
That did not stop him from registering runs of 66 and 52 to claim a 2-0 lead before breaks of 70 and 65 saw O'Sullivan take a 4-0 advantage into the mid-session interval.
Robertson got on the scoreboard with a well-worked 65 in the fifth set before a brilliant 116 break saw O'Sullivan regain his four-frame initiative and 998 career century.
The duo traded the next two frames and the Englishman improved his personal tally to 999 in the final frame of the afternoon session with a wonderful 105 for a 7-2 lead.
A 120 clearance helped Robertson cut the deficit to 7-3 in the opening frame of the evening session, however O'Sullivan came within inches of securing the landmark moment in the 11th frame.
O'Sullivan worked his way to build a neat 90 break but could not get position on the final red which was tight to the side cushion and his effort, while stretching with the rest, held up short in the jaws of the left corner pocket.
Robertson responded to reduce the score to 8-4 but O'Sullivan eased to the 13th frame to put himself within one of victory.
And 'The Rocket' claimed his 35th career ranking title and 1,000th century break in typical O'Sullivan style with standing ovation for every shot after surpassing the historic 100-point mark.