Gleeson also had some moments of uncertainty throughout the afternoon, but when he was given a kick in the sixth minute of stoppage time to seal the win, he impressively held his nerve to guide between the posts and lead a Mayo team to sink that looked ready to regain the title from the stands. end of normal time when Tommy Conroy had put them two points ahead, 0-15 to 0-13.
But Galway kept pressing and chasing and were rewarded with two Rob Finnerty free-kicks from close range for fouls on substitutes John Maher and Daniel O'Flaherty before Gleeson's coup de grace. Cillian O'Connor then had the chance to level the score, but it went wide.
Galway players Cillian McDaid, left, and Seán Kelly with the trophy after their side's victory in the Connacht SFC final against Mayo at the Pearse Stadium in Galway. Photo: Seb Daly/Sportfile
Mayo could raise issues over referee David Gough's award of Gleeson as Conor Loftus was surrounded by an aggressive press by Paul Conroy and Matthew Tierney after taking a kick from Colm Reape. But Gough was adamant and Gleeson stepped up to convert his second and most important free in a match riddled with mistakes.
But that won't concern Galway, for whom Damien Comer was the guiding light while Mayo could not stifle his power and movement.
David McBrien was tasked with following Comer but in this form he is unstoppable and with Rob Finnerty also in flying form, contributing eight points from play and cutter, Galway had a slight attacking edge.
For Joyce, the 2022 quarter-final at Castlebar was his only win in nine attempts in the Connacht League, League and Championship so far, so this redresses the balance somewhat and for the record it's a first Connacht final win over their neighbors in three attempts under his stewardship.
It also completes the province's first three-in-a-row in Connacht for 40 years and puts them in a group with the last losers of Ulster, Derry and Westmeath.
Joyce made two pre-game changes from the team announced earlier this week, replacing Maher and Shane Walsh with Kieran Molloy and Cathal Sweeney. But by the 33rd minute those changes had been reversed, a clear admission that they had not worked. Maher and Walsh both had strong impacts in the second half.
Mayo's Jordan Flynn in action against Galway's John Daly during the Connacht SFC final at Pearse Stadium in Galway. Photo: Daire Brennan/Sportsfile
Galway also struggled to get captain Seán Kelly into the game from centre-forward and Mayo had a decisive lead in the first half.
Comer was the obvious threat to that Mayo consolation, though, underlining that as early as the sixth minute, when taking on his marker David McBrien, he cut in along the backline and hit the side netting under enough pressure to create a to win a free ball.
It was one of three freebies Comer won for Rob Finnerty to convert in the first half, while he also added a point from play and scored a great save from Colm Reape in the 14th minute after setting up McBrien as he walked through with a nice ball. on its path through Finnerty.
But Mayo were largely in control for the half, even as a strengthening wind blew against them.
They simply had more energy during that period and their management felt it too, repeatedly urging them to storm Galway's defense.
When they did, gaps opened up, with Jack Carney running hard from midfield to create a few chances.
A lead of 0-7 to 0-5 seemed about where Mayo should be, but within minutes of the restart Galway had hit the front, 0-8 to 0-7.
That might have been more had it not been for some good defending from Rory Brickenden and Colm Reape to deny Maher a goal after Comer had set it home with a sharp move in the 39th minute.
Mayo hit the front again through Jordan Flynn, Matthew Ruane after Gleeson was caught in possession outfield and O'Donoghue on the loop from 45 yards.
But Galway did not go away and were level again, 0-11 each in 61 minutes, before leading 0-13 to 0-12 three minutes later through a Walsh point.
Mayo held steady and Conroy was centrally involved in the next three points, winning a free for O'Donoghue before landing the next two himself.
It looked like they could make it from there but Galway found a way with that impressive late surge.
Scorers – Galway: R Finnerty 0-8 (5fs), S Walsh 0-3 (1f), C Gleeson (2fs), D Comer 0-2 each, J Heaney 0-1. Mayo: R O'Donoghue 0-6 (4fs, 1m), M Ruane 0-3, T Conroy 0-2, J Flynn, F Boland, C O'Connor, D McHugh all 0-1 each
Galway: C Gleeson; J McGrath, S Fitzgerald, J Glynn; D McHugh, J Daly, L Silke; P Conroy, C Darcy; J Heaney, S Kelly, K Molloy; R Finnerty, D Comer, C Sweeney. subtitles: J Maher for Molloy (21), S Walsh for Sweeney (33), M Tierney for Heaney (52), S Mulkerrin for Fitzgerald (65), D O'Flaherty for Daly (71).
Mayo: C harvest; J Coyne, D McBrien, R Brickenden; E McLaughlin, D McHugh, S Callinan; J Carney, M Ruane; S Coen, F Bolan, J Flynn; T Conroy, A O'Shea, R O'Donoghue. subtitles: D O'Connor for Boland (45), C O'Connor for O'Shea (54), E Hession for Flynn (58), C Loftus for Coyne (65), B Tuohy for Carney (72).
Referee: D Gough (Meath).