British producer Ronson got his first number one with Uptown Funk on 14 December, and the single has now claimed the final top spot of 2014.
It was released five weeks early after it was performed by Fleur East on The X Factor, later topping the iTunes chart.
Haenow had topped the Christmas chart with OneRepublic's Something I Need.
Uptown Funk had dropped one place to make way for the former van driver's track over Christmas.
Fellow Briton Ed Sheeran, who scores a 12th week at the top of the album charts, held on to number three in the singles chart, with Thinking Out Loud.
American singer Taylor Swift moved up three places to fourth with Blank Space, while former X Factor star Olly Murs dropped one to fifth with Up, his collaboration with Demi Lovato.
The only new entry went to Alesso featuring Tove Lo with Heroes (We Could Be).
Sheeran's album logged sales of 211,000, his second biggest one-week sales tally since the LP's release back in June.
The top five was completed by Sam Smith, Murs, George Ezra and Take That, who all held their positions.
Mark Ronson's collaboration with Bruno Mars has reclaimed the number one spot in the singles chart, pushing X Factor winner Ben Haenow down to number two.