Fleetwood ties course record to grab lead in Abu Dhabi
Englishman Fleetwood made a flying start at Yas Links with birdies at the first and third holes either side of an eagle, and maintained his form throughout the round to finish ahead of Denmark's Thorbjorn Olesen and American Johannes Veerman.
Fleetwood picked up another shot on the seventh before making four birdies in five holes after the turn, closing out with his eighth birdie of the day at the last as he got up and down from the bunker.
"I got off to a great start, I actually didn't feel like I swung it perfectly early on and I felt like I swung it better as we got into the back nine," said Fleetwood.
"It was a lovely round of golf to play. Putted amazing, felt like I read the greens so well, beautiful pace control and hit a lot of perfect putts and started holing them.
"I'm just happy to have got off to a very good start."
Olesen also produced a bogey-free round that included eagles on the par-5 seventh and 11th holes, and a 43-foot putt for birdie on the 13th.
The Dane won on his last visit to the United Arab Emirates at the start of the year, claiming the Ras Al Khaimah Championship for his eighth and most recent European Tour title.
Veerman matched Olesen with a nine-under 63, his only blemish coming when he made bogey at the 12th after requiring three putts.
Tyrrell Hatton is among four players another stroke behind, while McIlroy is five shots off the pace as he chases a sixth Order of Merit title.
A win in Abu Dhabi would see McIlroy match the achievement of the legendary Spaniard Seve Ballesteros, before next week's Tour Championship.
Only Scotland's Colin Montgomerie (eight) has won more than Ballesteros.
McIlroy is currently leading the Race to Dubai standings, more than 1,500 points ahead of second-placed Thriston Lawrence of South Africa.
"I know that if I have a really good week this week, it makes my job a lot easier next week," said McIlroy.