Millwall's Emirates FA Cup journey ended at the Fourth Round stage on Saturday afternoon as Bristol City were 3-0 winners at The Den.
The Lions created chances against their Championship opponents, but were undone by a Famara Diedhiou penalty-kick and second-half goals from Nahki Wells and Antoine Semenyo.
Lions boss Gary Rowett made numerous changes for the visit of The Robins, with Frank Fielding starting in goal, whilst the likes of Tom Bradshaw, Shane Ferguson, Mahlon Romeo, Alex Pearce and Mason Bennett were also handed starts.
The opening stages saw the ball moved around in midfield without either side penetrating the opposition defence, but on nine minutes the first chance came - and it went the way of Millwall, but Bennett's shot was tipped wide by Max O'Leary. From the resulting corner-kick both Pearce and Bradshaw tried their luck, but the ball ended up in the arms of the stopper.
Five minutes later, Romeo was able to gallop down The Lions' right-hand side and cross for the head of Kenneth Zohore, but the striker's chance went over the crossbar. Bristol City's first opportunity, meanwhile, came with 18 minutes on the clock, but Tyreeq Bakinson skied his effort.
Bennett won the ball back on the halfway line for Millwall just one minute after that, but after Zohore charged down the left-hand side and crossed, Parrott's shot was gathered by O'Leary. Diedhiou then latched on to a delightful ball into the Millwall area, but the defence were able to crowd him out before he pulled the trigger, with the attacker eventually committing a foul.
The Lions were able to regain possession twice in midfield as the half-hour mark arrived, but Ryan Leonard's drive was well parried by O'Leary. However, just moments later, The Robins were awarded a penalty-kick after Fielding brought down Diedhiou in the area - the striker dusting himself down to take the kick and strike beyond the despairing dive of the goalkeeper.
Bradshaw's header was cleared off the line by Tommy Rowe as The Lions looked to respond instantly, but that clearance nearly proved pivotal as Bristol were able to break away through Semenyo - that attack turned into a cross for the head of goalscorer Diedhiou, but he glanced inches wide of Fielding's far post.
Bennett's shot was deflected and then tipped wide by O'Leary as the chances kept coming - particularly for Millwall - but the next attempt went the way of the visitors, with Fielding having to tip Nahki Wells' free-kick behind on the stroke of half-time.
Kasey Palmer's shot was charged down by Jake Cooper as the second-half got underway, with Pearce striking the next chance at the other end as his attempt was tipped over by O'Leary after space opened up for the centre-back to shoot.
With Millwall straining to get back into the game, on 58 minutes, they were dealt a sucker punch when Wells' free-kick deflected off the wall and bounced past Fielding to give The Robins a 2-0 lead.
Just four minutes later it looked as though the visitors had scored a third through Semenyo, but thankfully for The Lions, after another awful deflection took the ball away from Fielding and into the net, the assistant referee flagged for offside.
With 72 minutes on the clock, however, it was three as Semenyo broke through the last line of defence and finished well.
The Lions did almost claim one back straight after, but O'Leary saved well down low from Ben Thompson's powerful header. Romeo's cross was then headed over by substitute Matt Smith, but no further action meant that The Robins advanced to Round Five.
Millwall: Fielding, Cooper, Thompson (Woods 76'), Bradshaw, Ferguson, Romeo, Zohore (Smith 63'), Pearce, Leonard, Bennett (Skalak 76'), Parrott (Burey 63'). Subs not used: Bialkowski, Hutchinson, Malone, Bodvarsson, McNamara.
Bristol City: O'Leary, Diedhiou (Martin 75'), Semenyo (Adelakun 75'), Mariappa, Wells (Bell 87'), Kalas, Moore, Rowe, Vyner (Edwards 80'), Bakinson, Palmer (Massengo 75'). Subs not used: Bentley, Hunt, Nagy, Towler.
Scorer: Diedhiou pen 32', Wells 58', Semenyo 72'
Referee: Tony Harrington