With the prize of playing either Roma or new German champions Bayer Leverkusen at stake, neither side can afford to give ground at the iconic Stade Velodrome.
Match preview
Ultimately aiming to reach the final of either the Europa League - or its predecessor, the UEFA Cup - for a fourth time, Marseille have a rich tradition in continental competition, having lost in the 1999, 2004 and 2018 deciders after being crowned champions of Europe back in 1993.
More recently, the French giants were eliminated by Feyenoord at this stage of the 2021-22 Europa Conference League, and they have now made it through to this season's Europa League semis in the most dramatic of circumstances.
Burdened by a series of injuries and requiring academy players to fill in, Jean-Louis Gasset's side had suffered five straight defeats before taking on Benfica in the second leg of their quarter-final, but a 1-0 home win forced extra time: substitute Faris Moumbagna's late header kept OM in it, and after 30 more goalless minutes, they eventually prevailed 4-2 on penalties.
Shortly after being sacked mid-tournament by AFCON hosts Ivory Coast, Gasset stepped in to become Marseille's third manager of the season, after Marcelino and Gennaro Gattuso both failed to last the pace, and the veteran coach has succeeded in steadying the ship.
The Mediterranean coast club have still not escaped choppy waters, though, as Sunday's 2-1 win over Lens was their first in six Ligue 1 games: Pierre-Emerick Aubameyang's first-minute opener and Pape Gueye's late goal kept them in the hunt for European qualification.
Of course, winning the Europa League would provide a route straight into next term's new-look Champions League, but Atalanta stand in their way of making another final.
Having won their last five home games in UEFA competition but struggled on the road, gaining a first-leg advantage is surely essential ahead of next week's trip to Bergamo.
Following Sunday's 2-0 win over Empoli, secured by a Mario Pasalic penalty and Ademola Lookman's second-half strike, Atalanta have come out on top in 11 of their last 14 home matches across all competitions.
As if that were not enough to concern Marseille ahead of the second leg, the Italian side are also unbeaten in nine European away matches as they prepare for their springtime sojourn to Provence.
La Dea have already made Europe sit up and take notice by beating Liverpool 3-0 at Anfield in the quarter-finals, so Stade Velodrome should not hold too many fears, in spite of its notorious reputation.
After enduring a mid-season sticky spell, Atalanta have been on the up since their last-16 defeat of Sporting CP, and having just booked a place in the Coppa Italia final, they are also in the race to earn Champions League qualification via Serie A.
Gian Piero Gasperini's men sit sixth in the standings with five games remaining, and Italy's top flight has already assured five places at Europe's top table for next season - partly thanks to Atalanta and Roma reaching the Europa League semi-finals and boosting their national coefficient.
For all his previous achievements, 'Gasp' would surely consider leading La Dea out in their first European final the greatest: to date, the Bergamo club's biggest honour was winning the 1963 Coppa Italia, and they have now reached the semis of a UEFA tournament for just the second time.
They could even meet domestic rivals Roma in Dublin - both teams are also battling out for that fifth spot in Serie A - and then become the first Italian team to lift the Europa League trophy. However, two tough games against Marseille must be negotiated before such dreams can be realised.
Marseille Europa League form:
D
W
W
L
L
W
Marseille form (all competitions):
L
L
W
D
D
W
Atalanta BC Europa League form:
D
W
D
W
W
L
Atalanta BC form (all competitions):
W
D
L
W
W
W
Team News
While quarter-final hero Faris Moumbagna returns from suspension, having been replaced by Iliman Ndiaye against Lens last time out, Marseille must do without centre-back Samuel Gigot on Thursday evening, due to a one-match UEFA ban.
Fellow defender Chancel Mbemba was recently ruled out for the next few weeks by a knee injury, and Jean-Louis Gasset's list of absentees remains lengthy: Quentin Merlin (ankle) and Ismaila Sarr (hamstring) are still sidelined, alongside Bamo Meite and Valentin Rongier - the latter pair are out for the rest of this season.
The hosts can still call upon the Europa League's top assist-makers Jonathan Clauss and Amine Harit - both of whom have set up six goals in the competition this term - plus the tournament's all-time and current top scorer, Pierre-Emerick Aubameyang - the Gabon striker has netted 10 times en route to the semi-finals.
Meanwhile, Atalanta's top marksman in Europe this season is Gianluca Scamacca (five goals), and having recently starred in their Coppa Italia semi-final win over Fiorentina, he will battle it out for selection with Charles De Ketelaere, Ademola Lookman and El Bilal Toure up front.
The visitors also have one player suspended for the first leg, and Isak Hien's enforced absence should see Sead Kolasinac regain his place in Gian Piero Gasperini's back three.
Italy international Giorgio Scalvini returned to the lineup last weekend, after recovering from a hamstring problem, and will also feature in La Dea's defence; however, Emil Holm and Rafael Toloi are still unavailable.
Marseille possible starting lineup:
Lopez; Murillo, Gueye, Balerdi; Clauss, Harit, Veretout, Kondogbia, Garcia; Aubameyang, Moumbagna
Atalanta BC possible starting lineup:
Carnesecchi; Djimsiti, Scalvini, Kolasinac; Zappacosta, De Roon, Ederson, Ruggeri; Koopmeiners, Lookman; Scamacca
Fiorentina 
Udinese 
Benfica 
Estoril 
Inter 
Como 
Manchester City 
Everton 
Chelsea 
Fulham 
Nottingham Forest 
Tottenham 
Celtic 
Motherwell 
Wolverhampton 
Manchester Utd 
ST Mirren 
Rangers 
Sampdoria 
Carrarese 
Liverpool 
Leicester 
Arsenal 
Ipswich 
Cagliari 
Lazio 
Atalanta 
FC Porto 
Boavista 
Torino 
Napoli 
Venezia 
ST Johnstone 
Juventus 
West Ham 
Pisa 
AC Milan 
Roma 
Sporting CP 
Newcastle 
Brentford