The Norwegian striker netted in the 78th minute to give Enzo Maresca's side all three points after Leipzig had twice fought back to level the contest.
City took the lead in the 37th minute through an unfortunate own goal from Castello Lukeba. The Leipzig defender turned Nico O'Reilly's low cross into his own net under pressure from the visitors' attack.
Leipzig responded strongly after the break and equalised four minutes into the second half. Ridle Baku caught goalkeeper Gianluigi Donnarumma off guard with a clever finish from a tight angle following a pass from Brajan Gruda.
Manchester City restored their advantage in the 58th minute when Enzo Fernández powered a header into the net from Iliman Ndiaye's excellent cross.
However, the hosts needed only three minutes to respond. Antonio Nusa collected Christopher Nkunku's pass before driving a low shot into the bottom corner to make it 2-2.
With the contest finely balanced, City increased their attacking pressure and found the decisive goal in the 78th minute. Elliot Anderson delivered a low cross into the penalty area, allowing Haaland to slide the ball home from close range.
Leipzig pushed for another equaliser in the closing stages, with David Raum striking the crossbar from a free-kick. Rayan Cherki also hit the woodwork for City as the visitors held on for an important away victory.
City return to winning ways
The victory was an important response for Manchester City following their Premier League defeat against Brighton at the weekend.
Haaland's goal was his 13th against RB Leipzig in nine appearances, making the German side the opponent against whom he has scored the most goals in his career.
The result moved City up to seventh place in the Champions League league-phase standings, with three victories from their opening four matches.
Match details
• RB Leipzig: 2
• Manchester City: 3
• RB Leipzig scorers: Ridle Baku 49', Antonio Nusa 61'.
• Manchester City scorers: Castello Lukeba 37' (own goal), Enzo Fernández 58', Erling Haaland 78'.
• Competition: UEFA Champions League, League Phase, Matchday 4.
• Venue: Red Bull Arena, Leipzig.
• Date: Wednesday, 4 November 2026.
What's next for Manchester City?
Manchester City will return to Premier League action on Saturday, 7 November, when they travel to face Nottingham Forest.
Their next Champions League fixture will be against Napoli at the Etihad Stadium on Tuesday, 24 November.