Tennent's already boast a 35-year heritage of investment and support for football in Scotland, including an 18-year association with the Scottish Cup, the 'Tennent's Sixes' and most recently as sponsor of the Scotland national side.
Celtic say some of the cash from the deal will be used to help bolster the playing squad.
Chief executive Peter Lawwell said: "Celtic is delighted to enter into this new partnership with Tennent's, a brand which has become synonymous with football.
"In very challenging times for Scottish football, it is fantastic that Tennent's has maintained its high level of commitment to the game in Scotland, something they should be applauded for.
"This sponsorship provides important revenue for Celtic over the next three years, which will contribute to our continued investment in the football squad.
"We are sure this partnership with Tennent's will be most beneficial.'
Rangers chief executive Martin Bain said: "The Tennent's brand has been synonymous with Scottish football for decades and we are pleased they have chosen to take their sponsorship to a new level by investing in the Old Firm.
"We were extremely impressed by the vision and aspirations of the Tennent's team and we are confident this partnership will deliver on a number of levels.
"We look forward to forging a successful relationship with Scotland's leading lager brand over the next three seasons."
Tennent's managing director Mike Lees said: "Football is a national obsession in Scotland and we believe this partnership with Scotland's biggest and most successful football clubs takes our long-held strategy of sponsorship and investment in the game to the next level.
"We are very much looking forward to working with the clubs and their fans and to an exceptional year for the brand in 2010."
Meanwhile, Tennent's is continuing negotiations with the Scottish Football Association in relation to the national team.