ABERDEEN, July 10, 2014 (AFP) - McIlroy grabbed eight birdies, including four in succession mid-round, to break the existing course record by two shots with a seven under par 64 in bright but windy conditions on the par 71 links gem.
It handed the double Major winner, who is contesting the event for a first time in four years, a one-shot lead over Sweden's Kristoffer Broberg, the 27-year old Stockholm player equalling his best score on Tour with a six-under par 65.
In fact, Broberg had established a new low some two hours before McIlroy ended his round while Argentina's Ricardo Gonzalez had moved to eight under par when he eagled the 12th hole before bogeying two of his closing six holes in a 65 to join Broberg in a share of second.
McIlroy's score lowered the existing mark of triple Royal Aberdeen Club champion, Mark Halliday by two shots, and it adds to a growing number of course records on both sides of the Atlantic Ocean in the possession of the 25-year-old.
The pick of those is an Old Course record of 63 set on the opening day of the 2010 British Open and a similar score in the 2009 WGC-HSBC Champions event in Shanghai.
"It depends where it is whether or not setting a new course record is special to me but then there are a few that are a little better than the others," he said.
"I just hope nobody betters the 61 I shot at Royal Portrush as I have been holding onto that one for years.
"Regardless of the score, the way I played today was just the most pleasing thing and if I can play like that over these next few days going into next week, then that is what I need to do and the type of golf I have to play at Royal Liverpool (at the 2014 Open next week)."
McIlroy's impressive display off the tee was no better highlighted when he drove the green at the downwind 436-yard (399-metre) par four 13th and much to the amazement of the three ball in front that included defending champion Phil Mickelson, Luke Donald and Holland's Joost Luiten.
- Second-longest drive -
McIlroy's wind-assisted drive is believed to be the second longest in the history of the European Tour and just nine yards short of the 445-yard downhill effort of India's Shiv Kapur in the 2012 Madeira Islands Open.
Broberg had just 24 putts in his round and four less than McIlroy.
Two years ago the softly-spoken Swede made a big noise in rewriting the secondary Challenge Tour records in winning four events to secure his main European Tour card.
And while Broberg struggled last year in his rookie season with injury he has recently began to rekindle the form of two years ago, and virtually wrapping up his Tour card for 2015 with a share of third in the recent Irish Open.
"I played really, really well and I hit very good shots and a lot of close ones, so this helps a bit," he said.
Northern Ireland's Michael Hoey also showed his fondness for links golf to be fourth with a five under par 66.
Four players including Donald along with Scotland's Marc Warren, who let slip victory in the event two years ago at Castle Stuart, are well placed with four under par 67s.
Defending champion Phil Mickelson found himself in a tricky situation after a wayward drive at the 14th when his ball came to rest inches from a portable toilet.
The five-time Major winner was afforded relief, but with his ball landing on a bitumen pathway Mickelson had to play his next shot.
He hit the ball cleanly off the pathway and landed his shot to two feet from where he putted out for birdie in an eventual round of a three under par 68.
Leading first round scores in the Scottish Open at Royal Aberdeen, Aberdeen, Scotland on Thursday (par 71, GBR/IRL unless stated):
64 - Rory McIlroy
65 - Kristoffer Broberg (SWE), Ricardo Gonzalez (ARG)
66 - Michael Hoey
67 - Richard Bland, Luke Donald, Marc Warren, David Drysdale
68 - David Howell, Russell Knox, Phil Mickelson (USA), Kevin Phelan, Gary Stal (FRA)
69 - Paul Casey, Darren Clarke, Nicolas Colsaerts (BEL), Niclas Fasth (SWE), Matthew Fitzpatrick, Shiv Kapur (IND), Pablo Larrazabal (ESP), Matteo Manassero (ITA), Justin Rose, Tyrrell Hatton
70 - Simon Khan, Ryan Palmer (USA), Soren Kjeldsen (DEN), Graeme Storm, Gareth Maybin, Alastair Forsyth, Lucas Bjerregaard (DEN), Thomas Bjorn (DEN), Fabrizio Zanotti (PAR), Tommy Fleetwood, Martin Laird, Greig Hutcheon, Danny Willett, Jeev Milkha Singh (IND), Tom Lewis, Carlos Del Moral (ESP)