It is a contest that has the country in a state of excitement more usually associated with a match-up like last year's when great traditional rivals Dublin and Kerry clashed for the Sam Maguire Cup.
Donegal and Mayo have no great record of All-Ireland success, with Donegal winning just one in 1992 and Mayo three -- in 1936, '50 and '51. so, how can they overcome their lack of a winning tradition, something that is often touted as essential when you go to Croke Park on the big occasion?
The story of this dramatic reversal in fortunes has its origins in disastrous campaigns for both counties in 2010.
Donegal were whipped by Armagh in the first round of the Qualifiers by 2-14 to 0-10 and Mayo fared even worse, losing by 1-12 to 0-14 to Longford, who had been playing Division 4 football.
On the surface, not a great environment into which you would throw new, inexperienced managers.
But it is now quite clear that the first and main reason for the transformation rests with the respective bosses.
Jim McGuinness did get a dry run when in charge of the Donegal team that lost the All-Ireland U-21 final to Dublin, but James Horan emerged courtesy of an impressive performance that saw his home parish team Ballintubber win the Mayo senior championship.
Yet when they were appointed in 2010 there was no sign of the miracles that were to follow in 2012. And these two managers are very different in many ways.
McGuinness is a driven man -- he took total possession of the Donegal team, it became his own personal fiefdom and he devised a style of playing that guaranteed Donegal would not have to score a lot to win games, but, most importantly, he raised the bar for the players.
He only picked lads who were prepared to jettison the image of Donegal football that made the county a laughing stock for years. They were often regarded as talented, but lacking in many of the modern-day requirements for winning football games, such as total dedication, complete assimilation to the mindset of their manager and his draconian levels of discipline that shocked many outsiders and, indeed, many former Donegal players, too.
The steel that he wanted to instil into Donegal players was first implemented in himself last summer when he faced up to savage criticism by all and sundry about the style of play he enforced with Donegal. It was ultra-defensive in a manner that made Tyrone of 2003 onwards look almost icons of attacking play.
Up to 12 players were often seen in the Donegal defence, but always with a sense of purpose, initially, at least, to close shop and stop opponents from scoring freely. The nadir of this style, as far as the majority of Gaelic football followers was concerned, came in last year's All-Ireland semi-final when the final score was Dublin 0-8, Donegal 0-6.
It was a game that shocked the GAA public by the level of negativity it seemed to portray, but, as time went by, and the DVD was consulted over the winter, many began to see the nucleus of a brave, adventurous style emerging via McGuinness's fertile mind.
A winter of further experimentation followed in Division 1 where some variations on a theme were tried out and by championship time, a far more rounded Donegal team took the field that began to score freely while still retaining the core defensive values of 2011.
This has brought them all the way to the gates of the Promised Land.
Mayo's transformation was not as dramatic, largely because they did not have as many obstacles to climb in Connacht as Donegal had in Ulster. Horan retained the better aspects of Mayo football, but he, too, began to control the minds and bodies of the players in a manner not normal in that county -- though they had used psychologists in recent years.
Horan's main achievement was in recycling several players he inherited into transformed, mentally strong players. But then he also dug up several young or previously unused talent just as McGuinness has done with Donegal.
Young Cillian O'Connor came on board as a free-taker to get the show on the road and his skills helped to beat Roscommon, then Connacht champions. At the same time, Patrick McBrearty, even younger, came onto the Donegal team when he got a chance to finish his Leaving Cert, like O'Connor. Brave managers, bolder players.
With the great James Nallen finally retiring, Horan used the opportunity to bring in an almost new defence by trial and error, with the positioning of Donal Vaughan at centre half-back being the most critical decision.
Here at last was a Mayo No 6 who could stand his ground and flatten opponents legally when the opportunity arrived -- not previously a very common sight in Mayo backlines.
And just as McGuinness was fortunate to see the arrival of the immensely talented Michael Murphy, right on cue came Aidan O'Shea to match that brilliance and provide a great, natural midfielder for Mayo and with football brains, too.
Another fortunate development for both managers in recent weeks was the drawn All-Ireland hurling final, which has greatly reduced the media coverage leading up to the football final, even though they had both already done well in the hype-suppression stakes.
Between them these two managers have set a modern-day template for success in Gaelic football at county level. The fact that they are 'youngish' in GAA terms is neither here nor there. No, it is their application of modern sports science from all over the world, mainly sourced from professional sports, that has been the biggest factor.
That, plus, of course, their own innate ability to initiate, explain and implement THEIR plans for THEIR team is the reason why they are the talk of the country this week.