Roscommon and Mayo meet for the first time in a championship game in Croke Park (4pm).
But this occasionally testy rivalry has produced some legendary clashes in Connacht down the years. Below are five of the best.
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1989 Connacht Final replay
Mayo 3-14 Roscommon 2-13 (AET)
Before there was ever talk of a curse.
In the summer of 1989, Mayo's most recent memory (admittedly, not very recent) of an All-Ireland final was a victorious one and they were in the midst of restoring their status as a dominant force in Connacht after a relatively barren stretch over the previous few decades.
After strolling to Connacht success the previous year, their 1989 provincial campaign was a protracted one, requiring replays against both Galway and Roscommon.
The '89 replay between Roscommon and Mayo still stands out, against some stiff competition, as the craziest and most hectic of all Connacht deciders.
Trailing 1-11 to 1-09 in injury-time, Roscommon manufactured a penalty.
The silver-haired Tony McManus, a veteran of the 1980 All-Ireland final, coolly passed the ball to the net and the hosts looked to have regained the Nestor Cup.
However, from the very next attack, Micheal Cummins smashed home a goal for Mayo. He wheeled around to celebrate but quickly learned that Mayo had already been awarded a free on the 21 metre line.
Extra-time was required and the visitors stole the initiative, scoring critical goals in the second period.
Jimmy Burke sealed the deal at the death for Mayo with one of the most inelegant finishes in the history of sport, any sport.
It made Anthony Finnerty's goal earlier in extra-time, hardly a thing of beauty, look like of a virtual goal of the championship contender.
But no matter. Mayo had retained the Nestor Cup. They had fallen to the all-conquering Meath in the '88 semi-final but Tyrone lay in wait in the August '89 semi-final.
And this being the era when Ulster and Connacht were very much the poor relation in football, it offered them a glorious chance of progressing to September.
1991 Connacht Final replay
Roscommon 0-13 Mayo 1-09
The late '80s and early '90s marked the golden era of Mayo-Roscommon epics.
Derek Duggan's monstrous free-kick at the end of the 1991 Connacht final in McHale Park rescued a draw for Roscommon and gave them a chance of another tilt at back-to-back provincial titles a week later.
Duggan was a central figure again in the replay, nailing 0-8 from Roscommon's winning tally of 0-13.
For 2017 watchers, the game is especially notable for Mayo's jinking corner-forward Kevin McStay lobbing over a beautiful point in the first half.
Roscommon dominated the first half and held Mayo at arm's length until the fraught closing stages when compulsive goal-getter Anthony Finnerty was allowed away with a blatant push in the back on Des Newton before he slotting the ball to the net.
However, Roscommon finished the stronger with the elegant midfielder John Newton swerving over a point to level the game. And it was the nerveless Duggan who decided the destination of the Nestor Cup once more with a late free.
1992 Connacht Final
Mayo 1-13 Roscommon 0-09
We haven't exactly conducted an exhaustive study on this but it can be safely assumed that this is the only Connacht final to ever feature on an episode of A Question of Sport.
Roscommon corner back Enon Gavin pulling down the crossbar early in the second half puzzled Ally McCoist and co. during the 'What Happened Next?' segment.
Anthony Finnerty collected a pass, darted inside an onrushing defender and squeezed a shot away from close range.
Veteran goalkeeper Gay Sheerin partly blocked the shot but it ricocheted off his body and looped into the air, eventually landing on top of the crossbar and hopping over for a point.
In a spirited but vain attempt to prevent the score, All Star defender Gavin dived into the Roscommon goalmouth and swung off the crossbar which promptly snapped in two.
The game was delayed by seven minutes while a new crossbar was erected. After the match resumed Mayo took complete control, outscoring the Rossies 0-08 to 0-02 for the remainder of the game.
In a widely seen Facebook post over two decades later, the Mayo minor goalkeeper Donal Hughes claimed responsibility for the incident, citing his penchant for nonchalantly swinging from the crossbar whenever an opposition score was kicked.
He did so during the minor game that day only for his acrobatics to cause the crossbar to crack and drop slightly. He was admonished by the umpire but the minor referee inspected the goalposts at half-time and deemed them robust enough.
Alas, that same crossbar wouldn't survive the senior game.
2001 Connacht Final
Roscommon 2-10 Mayo 1-12
Of Roscommon's last five provincial triumphs ('90, '91, '01, '10, '17) this is the only one which incorporated wins over both Mayo and Galway en route. (Indeed, their 2010 Nestor Cup win required them to beat neither of the traditional western powers.)
Teenage midfielder Seamus O'Neill was the breakout star of that year's Connacht championship, thoroughly dominating Galway's All-Ireland winning midfield duo of Kevin Walsh and Sean O'Domhnaill in the Tuam semi-final.
However, he very nearly become the villain a month later in Hyde Park. With Roscommon leading Mayo 1-10 to 0-12 in injury time, O'Neill chose to stand still and wait for a Clifford McDonald fist-pass to arrive into his chest forty metres out from his own goal.
David Brady nipped in to intercept and he fed David Nestor who cut inside and slammed a shot past Derek Thompson.
John Tobin's side appeared to have been denied at the death but from the very next attack Jonathan Dunning won a free in the panicky final seconds (as he would in the 2010 provincial final).
He took it quickly and began a move which ended with Gerry Lohan blasting home his second goal of the match and delivering Roscommon their first Connacht title in ten years.
It was a sweet provincial victory, albeit one which was somewhat soured by their rather underwhelming All-Ireland quarter-final experience.
It was the first year of the current All-Ireland qualifier format and Croke Park was not yet installed as the obligatory venue for All-Ireland quarter-finals. Nor were teams yet precluded from meeting sides they'd already beaten in the championship in the quarter-final.
Thus, their rather paltry reward for winning a Connacht title was meeting Galway again, this time in Castlebar.
2014 Connacht semi-final
Mayo 0-13 Roscommon 1-09
Since Roscommon's dramatic win in the 2001 Connacht final, Mayo have won six on the trot against the Rossies in the championship.
A couple of those wins have been a touch one-sided, especially the 2009 Connacht semi-final, a game which the entire Roscommon squad and backroom staff will want to wipe from their memory bank.
Suffice to say, a half-time scoreline of 3-10 to 0-01 will tell those who've forgotten about the match all they need to know. The game represented the nadir of Roscommon's grim years in the late noughties.
But Roscommon did almost spring the perfect ambush against a far more highly regarded Mayo side five years later.
With James Horan's side still close to their peak, Roscommon had them on the rack into the final ten minutes of this early summer encounter.
After a low-scoring first half, Roscommon wing-back Ciaran Cafferkey slipped home a goal to give the hosts the lead on the 42nd minute.
They would retain this advantage until the final five minutes of normal time.
But inspirational late scores from Andy Moran, Seamus O'Shea and Kevin McLoughlin steadied Mayo nerves and enabled them to power on to victory.
Kerry v Galway (2pm) and Roscommon v Mayo (4pm) will be live on RTÉ2 and RTÉ Radio 1's Sunday Sport with a live blog on RTÉ Sport Online and the News Now App. Highlights of all the weekend's GAA action on The Sunday Game from 9.30pm on RTÉ2.
