The Reds twice took the lead through Trey Nyoni and substitute Alexander Isak, but defensive lapses allowed the Turkish hosts to fight back and claim all three points.
Liverpool made a positive start and broke the deadlock in the 25th minute through 19-year-old Nyoni. The midfielder fired home a volley after Rio Ngumoha's delivery caused problems in the Fenerbahçe defence.
However, the visitors' advantage lasted only four minutes. Mason Greenwood equalised in the 29th minute when his free-kick took a significant deflection off Liverpool defender Jeremy Jacquet, leaving goalkeeper Alisson Becker unable to make the save.
The teams went into the break level after an entertaining first half.
Liverpool regained the lead in the 69th minute through Isak, who had just come on as a substitute. The Swedish striker headed home Cody Gakpo's cross with his first touch to put the visitors 2-1 ahead.
Fenerbahçe responded almost immediately, restoring parity in the 73rd minute through Archie Brown, who capitalised on defensive confusion inside Liverpool's penalty area.
The hosts completed their comeback six minutes later. Vedat Muriqi rose above the Liverpool defence to head home in the 79th minute, giving Fenerbahçe a 3-2 advantage.
Liverpool struggled to find another equaliser as Fenerbahçe held on to secure a memorable victory in front of their home supporters.
Liverpool's perfect European start comes to an end
The defeat ended Liverpool's winning start to the Champions League league phase after three consecutive victories.
The result leaves the Reds with nine points from four matches, while Fenerbahçe secured their first victory of the campaign.
Liverpool manager Andoni Iraola will be disappointed with his team's defensive performance, particularly their inability to protect two separate leads.
Match details
• Fenerbahçe: 3
• Liverpool: 2
• Fenerbahçe scorers: Mason Greenwood 29', Archie Brown 73', Vedat Muriqi 79'.
• Liverpool scorers: Trey Nyoni 25', Alexander Isak 69'.
• Competition: UEFA Champions League, League Phase, Matchday 4.
• Venue: Şükrü Saracoğlu Stadium, Istanbul.
• Date: Wednesday, 4 November 2026.