Ten-man Cork City went back top of the SSE Airtricity League First Division after somehow prevailing at Eamonn Deacy Park, thanks to a stunning Matt Healy goal.
John Caulfield saw his former side win despite barely creating a chance on goal, but United lacked the quality to take advantage of endless possession.
The game was played in beautiful sunshine before around 5,000 fans, a real throwback to the old days when Cork City were a force, which they usually are, and Galway United were in the top flight, which they tend not to be.
The first half, in truth, was not for the purists – bar the goal that separated them, and it was quite something.
United found it difficult to face the sliding sun at the old dressing room end, City, by contrast, could aim at goal without distraction and their opener was world class.
Rory Keating had Conor Kearns scrambling, facing an old ally, before Healy's stunner on 18 minutes.
He picked up the ball around 25 yards out and curled spectacularly into the top corner, with Kearns having no chance.
United rallied and should have been level by half-time, but they would have to wait for what might come.
Conor McCormack blasted over on 22 minutes against his former club before the home fans were celebrating in vain five minutes later.
Ed McCarthy crossed and, with David Harrington beaten, Wilson Waweru's header was somehow cleared off the line.
Diego Portillo had ridden his luck with an ill-advised challenge on Cian Murphy in the box beforehand, so it was a two-way debate.
Right at the death, the lively Max Hemmings found space to cross only for Wawero to head wide.
The ever-dangerous Wilson looked for a penalty before the break but Oliver Moran hadn't seen enough.
Again it was the local striker Waweru who had space to shoot early in the second half after nice build up, but he was just off target.
Fifteen minutes in and it was all United. Manu Dimas, who came in at the interval, hooked wide when attempting to cross, with Harrington uncertain.
Midway through the half, there was something to give United more hope. Waweru had just missed a great chance and, as City broke, they won a free. Off the ball, Keating was sent off after an altercation with Portilla.
United couldn't make much of the added player, with McCormack blasting over at the death.
Galway United: Kearns; Hemmings (Lomboto 81), Portilla (O'Keeffe 77), Brouder, Murphy; McCormack, Hurley; McCarthy (Manning 78), Boylan (Dimas 46), Waweru (Adeyemo 85); Walsh.
Cork City: Harrington; Bargary (Hurley 82), Hakkinen, Gilchrist, Honohan, O'Connor; Healy (Crowley 87), Bolger, Coleman; Keating, Murphy.
Referee: Oliver Moran.
Elsewhere Waterford stayed third after a 4-0 defeat of Treaty United at the RSC.
It was scoreless at the break but the hosts went up a few gears on the turnaround.
Louis Britton put them ahead on 51 minutes and Roland Idowu made it two 12 minutes later following really good work by Phoenix Patterson.
It was 3-0 in the 66th minute - Shane Grffin slotting home after an excellent Patterson assist - and Cian Kavanagh put they cherry on top in stoppage time with a header.
Longford Town won a topsy-turvy game at Cobh Ramblers 4-2.
Pierce Phillps put Rambles ahead in the ninth minute, but seven minutes later Longford levelled through a Dylan Barnett penalty.
Cristian Magerusan headed Longford in front four minutes into the second half, and then backheeled Aaron Robinson in to fire home a third on the hour.
A Jake Hegarty cross-cum-shot gave Cobh Ramblers a lifeline just two minutes later, but Shane Elworthy restored the two-goal cushion in the 66th minute as Longford saw it out.
Bray Wanderers enjoyed a 3-0 victory against bottom club Athlone Town.
Darragh Lynch broke the deadlock on 19 minutes, then struck again in the 64th. Rob Manley's 74th effort then made sure of a first home win of the season for Bray.
