Both clubs narrowly avoided upsets against second-tier opposition in the last round and now find themselves just 90 minutes away from the final of the world's oldest cup competition.
The EFL Cup has already been won, the Premier League title remains in their hands and they have reached the quarter-finals of the Champions League.
Pep Guardiola's 'impossible dream' of the quadruple is edging ever closer with each passing week, and a 14th successive victory this weekend would leave the English champions within touching distance of one more leg of it.
The City players will no doubt run out at Wembley with warnings from Guardiola ringing in their ears, though; the next eight days could wreck their hopes in all three remaining competitions if things go badly, with Tottenham Hotspur to come on Tuesday in the first leg of their Champions League quarter-final and then a visit to Crystal Palace - who beat them at the Etihad earlier this season - in the Premier League next weekend.
City will go into all of those matches as favourites, particularly this weekend, but they only need to look at their own recent FA Cup history - yet alone the competition's giant-killing reputation - for evidence that they cannot afford to take Brighton lightly.
The quadruple quest almost ended on a rainy evening in Wales last month when Championship side Swansea City stormed into a 2-0 lead in the quarter-finals, only for Man City to score three times in the final 21 minutes to turn things around - although the final two goals arguably would not have stood had VAR been in play.
The fifth-round defeat to League One Wigan Athletic last season will also serve as a reminder that there are no gimmes in this competition, although Guardiola has certainly taken it seriously this season as he bids to land the only domestic trophy that has eluded him in his illustrious managerial career so far.
The Swansea scare was a blip in an otherwise destructive run to the semi-finals which has seen Man City hammer Rotherham United, Burnley and Newport County, scoring a competition-high 19 goals en route to Wembley.
City have not scored 20 times in an FA Cup campaign since 1981, when incidentally they made it to the final - one of 10 occasions from 13 previous semis that they have reached the showpiece of this competition.
The most recent of those successes came back in 2013, though, and the last time they lifted the trophy was in 2011 - a surprisingly long wait considering how much of a force they have been in the intervening eight years.
The current crop are well placed to end that wait this year, though, and show no signs of slowing down on any front as they charge towards English football history.
Recent FA Cup form: WWWW
Recent form (all competitions): WWWWWW
Man City are not the only team for whom history beckons this season, and Brighton will go into Saturday's match with their eyes set on lifting the famous FA Cup trophy for the very first time.
Indeed, they have never won any major silverware before, so victory this year would surely rank as the greatest moment in the club's 118-year history.
However, to do that they must traverse the mountain that is Man City, and Chris Hughton will be under no illusions of the size of the task that awaits his side this weekend.
It was a Manchester club that beat them in the 1983 FA Cup final - the only previous occasion that the Seagulls have made it as far as the semis before the current campaign - and they face an even more difficult test to reach the showpiece again.
Brighton were very nearly absent from the draw altogether, but like Man City they came from two goals down away to Championship opposition to seal their semi-final place in the most dramatic fashion.
Millwall seemed destined for Wembley when they led 2-0 heading into the 88th minute at The Den, but Jurgen Locadia pulled one back for the Seagulls before Solly March forced extra time - and eventually penalties - with a 95th-minute equaliser.
The subsequent shootout win sees Brighton become only the third club to reach the semi-finals via penalties, although their road to Wembley has been far less convincing than Man City's.
A third-round win at Bournemouth is as comfortable as it has been for Hughton's side, who have since needed a replay and extra time to beat West Bromwich Albion, scraped past Derby County and overcome Millwall on penalties - a trio of Championship sides to have made things difficult for the Premier League outfit.
The significance of Brighton still having work to do to retain their top-flight status should not be ignored either; Albion are currently five points clear of the dropzone but could still need two wins to guarantee their safety.
Hughton's side have also lost both games without scoring since booking their place in the semi-finals, being beaten at home by Southampton before falling to a convincing 3-0 defeat at the hands of Chelsea in midweek.
Not many would have been expecting Brighton to get anything at Stamford Bridge, but the same is true of this weekend at Wembley and the Seagulls - without a win in any of their last four matches at the national stadium - must do a better job of trying to upset the odds this time around.
Recent FA Cup form: WDWWW
Recent form (all competitions): LWWWLL
Man City top-scorer Sergio Aguero could recover from the muscle problem which kept him out against Cardiff City in midweek and has a formidable record in this competition, having scored 18 goals and created four more in 20 FA Cup outings.
However, Guardiola could opt to hold the Argentine back for next week's Champions League tie with Tottenham instead, leaving Gabriel Jesus to lead the line once more.
Oleksandr Zinchenko's injury against the Bluebirds leaves City short of options at left-back, and Danilo could be forced to fill in with Benjamin Mendy unlikely to be thrown straight back into the starting lineup after another injury-plagued campaign.
The enforced Zinchenko withdrawal was the only substitution Guardiola made in midweek, which suggests that changes could be in the offing with the likes of Raheem Sterling, Bernardo Silva and David Silva among the players who could come in.
Phil Foden will be hopeful of having done enough to keep his place, though, while Vincent Kompany could come in at centre-back as Guardiola rests other key players such as Aymeric Laporte, Fernandinho and Kevin De Bruyne.
Brighton, meanwhile, are hopeful that their goalscorers from the last round Locadia and March both recover from calf problems, with the latter having been forced off shortly after the half-hour mark against Chelsea.
Man City possible starting lineup:
Ederson; Walker, Kompany, Otamendi, Danilo; D Silva, Gundogan, Foden; Bernardo, Jesus, Sterling
Brighton possible starting lineup:
Ryan; Montoya, Duffy, Dunk, Bernardo; Propper, Stephens, Bissouma; Jahanbakhsh, Murray, Knockaert
Head To Head
Man City have won all three meetings between the two sides since Brighton were promoted to the Premier League, including a 2-0 win at the Etihad Stadium earlier this season.
Brighton have the edge in cup competitions, though, with one win apiece in the FA Cup and the Seagulls coming out on top on penalties in a 2008 League Cup clash.
The last time these two sides met in this competition was in 1983, when Brighton thrashed Man City 4-0 en route to their only previous final.
We say: Man City 2-0 Brighton
It is hard to bet against Man City in any game at the moment, particularly one for which they are such heavy favourites. Brighton rarely make it easy for teams under Hughton, but ultimately we expect quality to shine through and Man City to reach the final.
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