The pair's track first hit the chart back in December and spent a total of seven weeks at number one.
'Uptown Funk' has already hit the 1.44 million sales mark in combined sales this year alone, bringing its overall total to 1.93 million.
Hozier's 'Take Me To Church' follows as the second biggest song after selling 996,000 copies and is the only entry in the Top 5 to not actually take the number one spot in the weekly chart.
The single's success built up after a 20-week chart climb, before peaking at number two, where it stayed for two weeks.
OMI's 'Cheerleader' is not far behind at three with 994,000 sales, while Ellie Goulding's 'Love Me Like You Do' is at number four with 983,000 sales and Wiz Khalifa ft Charlie Puth's 'See You Again' is at five with 857,000 sales since it was released in April.
See the top ten biggest songs of 2015 so far in full below:
1. 'Uptown Funk' - Mark Ronson ft Bruno Mars
2. 'Take Me To Church' - Hozier
3. 'Cheerleader (Felix Jaehn Remix)' - OMI
4. 'Love Me Like You Do' - Ellie Goulding
5. 'See You Again' - Wiz Khalifa ft Charlie Puth
6. 'Hold Back the River' - James Bay
7. 'Four Five Seconds' - Rihanna, Kanye West and Paul McCartney
8. 'Sugar' - Maroon 5
9. 'King' - Years & Years
10. 'Thinking Out Loud' - Ed Sheeran
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