The song, which features Bruno Mars, was due out in January.
The British DJ and producer changed the date after it was performed on the X Factor on Saturday.
Contestant Fleur East's version of the song spent three days on top of the iTunes chart before being trumped by Ronson's original.
Uptown Funk is the first single from Ronson's Uptown Special album which is due out next year.
Fleur East admitted that she performed the song after being handed it a just hours before the live show.
She said: "I don't think anyone expected my performance to be as popular as it was.
"We didn't expect it to go to number one on iTunes. That's crazy like."
Seemingly wanting to benefit from the hype generated by Fleur, Mark Ronson, bought forward the song's release date.
X Factor boss Simon Cowell and Mark Ronson are both under the Columbia Records umbrella and critics have suggested this is a clever PR move.
Changing the release date of the song was seen as a gamble by some.
Uptown Funk has entered the charts at the most competitive time of year - the race for Christmas number one.
Although some bookmakers have suspended bets on the song staying on top of the charts over the festive period.
However it faces competition from the Band Aid charity single and the X Factor's winner's single - which ironically could belong Fleur.
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Mark Ronson was forced to release Uptown Funk five weeks early but that hasn't stopped the track racing to the top of the Official Singles Chart.