The multi-million three year deal will see the Scottish Premier League champions sport the Magners logo on their shirts from the start of the 2013/14 season.
Celtic and Rangers have had the same backer for the majority of the last 30 years, an arrangement that first started in the early 1980s when glazing firm CR Smith became the first company to sponsor them both.
Tennent’s, which announced a three year sponsorship deal with Celtic and Rangers in 2010, is thought to be in discussions with Rangers over a new deal.
Sponsorship experts say the Rangers tie-up with Magners could alienate some Rangers fans,
Nigel Currie, director of sports marketing and sponsorship at Brand Rapport, says: “There is such an intense rivalry between the two clubs that sponsors have always been conscious of not alienating either set of fans by choosing sides. If it is being done for intentional reasons then you can see some logic in that but Magners need to be careful about how they communicate the partnership to Scottish fans once the deal starts.
The sponsorship deal is not Magners’ first foray into the world of sport and the brand has previously sponsored several rugby union clubs as well as annual Rugby Union competition the Magners League.
A spokesman for Magners said the deal would give the Irish cider brand a lift in emerging markets as it looks to expand its global footprint.
He adds: “Magners is a premium brand with huge ambition both at home and abroad, available in over 40 markets worldwide including key cider growth territories like the US, Australia, Canada and Asia.”
The deal comes just days after Chevrolet, which sponsors both Manchester United and Liverpool, was criticised by the club’s fans for a perceived failure to understand the rivalry between the two following the launch of an online advert starring players from both teams.