Ryan Christie scoring his late penalty for ScotlandScotland need a point away to Ukraine on Tuesday to win Nations League Group B1 after a dogged comeback victory over the Republic of Ireland at Hampden.
John Egan volleyed Ireland ahead early on, but Jack Hendry's header levelled.
Both sides spurned big chances before Alan Browne was penalised for handball and Ryan Christie stroked home the penalty winner eight minutes from time.
That puts Steve Clarke's side two points clear of Ukraine, who briefly went top with a 5-0 win in Armenia.
However, Scotland head into their final group game in Krakow, Poland, with more injuries worries after full-backs Kieran Tierney and Aaron Hickey were both forced off, while a late yellow card for Scott McTominay rules the midfielder out through suspension.
Ireland, meanwhile, can now finish no higher than third in the group.
Scotland were buoyed by Wednesday's 3-0 win over Ukraine at Hampden. But with that dominant performance came expectation they would simply roll over an Irish side who three months earlier had handed them a chastening 3-0 defeat.
And a loud and confident Hampden was silenced when Troy Parrott slalomed through the Scotland defence and hammered the ball high into the net. The assistant referee's flag cut short the celebrations, but Ireland were again threatening to spring a shock.
Soon the visitors broke on the counter-attack and got two v two. Hendry blocked Parrott's effort, but it only delayed the opener.
Set-plays had been Scotland's downfall in Dublin and the frailty resurfaced. They struggled to clear a corner, the ball fell to Egan who lashed the ball through a ruck of bodies and past Craig Gordon.
Clarke's men had fallen apart in Dublin, but this time they responded strongly. The ball wouldn't fall for Stuart Armstrong and Lyndon Dykes in the box, while John McGinn mis-hit a shot wide, but the anticipation around Hampden was rising as the home side continued to pour forward.
And four minutes into the second half Scotland were level. Matt Doherty allowed Christie to breeze past him all too easily, and Hendry met his delivery to guide a header into the far corner via the post.
Doherty could have made amends at the other end when Greg Taylor was caught in possession, but he curled wide. Scotland's McGinn thumped past the post too as the game promised another goal.
And that should have arrived when Ireland pulled the hosts apart. From Scotland's corner, Callum McGregor coughed up possession, the Irish broke two on one, Michael Obafemi laid the ball into the path of Parrott who saw the whites of Gordon's eyes but shot straight at him.
Then a Gordon clearance bounced off Chiedozie Ogbene but back into the hands of the grateful goalkeeper. It was all Scotland possession, but Ireland were the ones passing up the chances.
The momentum shifted again in Scotland's favour. Ryan Fraser had a shot tipped over and Doherty defended brilliantly to head the ball away from McTominay.
Just as Scotland's frustration grew as the winner looked to elude them, they were gifted a penalty when the hand of Browne diverted the ball from McTominay's path in the box.
After a video assistant referee check, Christie slotted the penalty down the middle to bring Hampden to its feet. Ireland threw everything at Scotland in an attempt to find an equaliser but found a defence just as desperate to hold on.
Man of the match - Jack Hendry
His defensive performance alone was enough to win the award, but he capped it with the equaliser to get Scotland back into the matchDogged Scotland find a way - analysis
It was not the same flowing football from Wednesday, but the 90 minutes was just as pulsating as Scotland made it three straight wins.
Scotland's joy against Ukraine had come from their marauding full-backs and clever movement up front.
Tactically, though, Ireland were smart. Their two strikers pinned Scotland's wide players back, they defended their corners where Scotland had late joy in midweek. And despite Scotland having the lion's share of possession the Irish repeatedly found opportunities of their own.
It was a match that could have gone either way, but a penalty settled it.
Scotland did not have it all their own way as they did on Wednesday, but the confidence will be sky high before their rematch with Ukraine on Tuesday where Nations League promotion and a Euro 2024 play-off place are at stake.
What's next?
Group B1 concludes on Tuesday, as Scotland take on Ukraine in Krakow, Poland (19:45 BST) and Republic of Ireland host Armenia at the same time.
Match stats
Scotland are unbeaten in all eight of their home games in the Nations League (W7 D1) - no team has played more at home without ever losing in the competition (Italy also 8).Republic of Ireland are winless in all seven of their away games in the competition (D2 L5), losing each of the last four.Both teams scored with their first shots on target - for Scotland it was just the second time they'd conceded first in a home game in the Nations League (also v Israel in 2018), while it was the first time Ireland had scored first in an away game in the competition.In his 33rd appearance for Scotland, Ryan Christie both scored and assisted a goal in the same game for the first time at international level.Jack Hendry completed all 60 of his passes - the most a player has made while maintaining a 100% pass accuracy in this edition of the Nations League.John McGinn has created more chances (12) and had more shots (19) than any other Scotland player at this edition of the Nations League, with the midfielder having a further three of each against Ireland.Line-ups
Scotland
Formation 4-2-3-1
1Gordon
22Hickey13Hendry15McKenna6Tierney
4McTominay8McGregor
17S Armstrong7McGinn11Christie
9Dykes
1Gordon22HickeySubstituted forRalstonat 59'minutes13Hendry15McKennaBooked at 63mins6TierneySubstituted forTaylorat 42'minutes4McTominayBooked at 87mins8McGregor17S ArmstrongSubstituted forFraserat 59'minutes7McGinn11ChristieSubstituted forMcLeanat 85'minutes9DykesSubstituted forAdamsat 85'minutesSubstitutes
2Gallagher3Taylor5Porteous10Adams12Kelly14Gilmour16Ralston18Doig19Fraser20Jack21McCrorie23McLeanR. of Ireland
Formation 3-5-2
1Bazunu
12Collins5Egan18O'Shea
3Doherty15Molumby6Cullen17Knight11McClean
9Obafemi10Parrott
1Bazunu12Collins5EganBooked at 73mins18O'Shea3DohertySubstituted forColemanat 76'minutesBooked at 81mins15MolumbySubstituted forBrowneat 77'minutes6CullenBooked at 45mins17KnightBooked at 87mins11McCleanSubstituted forBradyat 83'minutesBooked at 90mins9ObafemiSubstituted forOgbeneat 60'minutes10ParrottSubstituted forRobinsonat 77'minutesSubstitutes
2Coleman4Duffy7Robinson8Hourihane13Hendrick14Browne16Travers19Hogan20Ogbene21Brady22O'Dowda23O'LearyLive Text
Match ends, Scotland 2, Republic of Ireland 1.
Second Half ends, Scotland 2, Republic of Ireland 1.
Corner, Scotland. Conceded by Robbie Brady.
Robbie Brady (Republic of Ireland) is shown the yellow card for a bad foul.
Ryan Fraser (Scotland) wins a free kick on the right wing.
Foul by Robbie Brady (Republic of Ireland).
Attempt saved. Jason Knight (Republic of Ireland) header from the centre of the box is saved in the bottom left corner. Assisted by Callum Robinson with a cross.
Attempt saved. Séamus Coleman (Republic of Ireland) right footed shot from the centre of the box is saved in the top left corner. Assisted by Robbie Brady with a cross.
Foul by Che Adams (Scotland).
Nathan Collins (Republic of Ireland) wins a free kick in the defensive half.
Attempt missed. Ryan Fraser (Scotland) right footed shot from outside the box misses to the right. Assisted by John McGinn following a fast break.
Corner, Republic of Ireland. Conceded by Anthony Ralston.
Scott McTominay (Scotland) is shown the yellow card.
Jason Knight (Republic of Ireland) is shown the yellow card.
Foul by John McGinn (Scotland).
Josh Cullen (Republic of Ireland) wins a free kick in the defensive half.
Substitution, Scotland. Che Adams replaces Lyndon Dykes.
Substitution, Scotland. Kenny McLean replaces Ryan Christie.
Foul by Scott McTominay (Scotland).
Robbie Brady (Republic of Ireland) wins a free kick in the defensive half.
