Jordan Spence's late header secured a dramatic 4-3 victory for high-flying Ipswich as they maintained their 100 per cent start to the Sky Bet Championship at Millwall.
The Tractor Boys have now made their best start to a campaign since they last won promotion to the Premier League 17 years ago and this third straight win will be even sweeter after Millwall thought they had snatched a point.
Jed Wallace fired Millwall ahead inside 44 seconds, but Joe Garner and Martyn Waghorn turned the game around for Ipswich before Aiden O'Brien equalised for the hosts.
Waghorn added his second on the stroke of half-time before Tom Elliott levelled again with 10 minutes left, only for Spence to nod in David McGoldrick's free-kick in the 88th minute.
Confident Ipswich boss Mick McCarthy started strikers Waghorn and McGoldrick at The Den, following their match-winning cameo in tandem as substitutes at Barnsley on Saturday.
But Millwall, who had lost just one of their previous 19 home games, took the lead within a minute as a deep cross from the left was only half-cleared to Wallace who thumped home via a deflection.
Ipswich levelled three minutes later through Garner's long-range strike, which was too hot for Jordan Archer to handle.
But Millwall's confidence was not affected and O'Brien missed a glorious chance to regain the lead by stabbing over the bar from seven yards.
The Lions remained on top for much of the half, starving Ipswich's attack, but McCarthy's pacey forward line only needed one chance to regain the lead in the 34th minute.
Millwall right-back Conor McLaughlin lost the ball inside his own half and McGoldrick scampered down the left and picked out Waghorn, who powered in emphatically following a fine run to the near post.
The hosts' heads could have dropped but they rallied impressively and were level two minutes later as O'Brien's clever overhead kick found the net after George Saville cracked the bar from close range.
The game became stretched as both sides surged forwards looking for a half-time lead, and Ipswich found it as McGoldrick waltzed his way through Millwall's porous defence and crossed again for Waghorn to turn it in.
Ipswich sat deeper in the second half as Millwall pushed forwards, and the Lions thought they had earned a point when substitute Elliott fired in at the back post from a deep free-kick.
But Spence leapt high to glance in McGoldrick's free-kick to win it for the visitors.