The Swans started the game strong until at the end of the first half Ryan Manning was sent off for a foul on Harry Wilson.
Aleksandar Mitrovic put Fulham ahead 14 seconds into the second half, before an own goal from Ben Brancho made it two. then Bobby Decordova-Reid added a third after Joel Piroe had headed in for Swansea, before Fulham's fourth goal was scored by Neco Williams before unleashing a stunning fifth.
The Championship leaders have now scored 89 goals in 35 games this season, with Mitrovic's 35 goals in just 33 appearances. And more importantly in terms of Fulham's promotion aspirations, Bournemouth's draw with bottom side Peterborough United means the Cottagers are now increasingly clear at the top of the table.
The Swans kept possession well and maneuvered through Fulham's pressure but it was the visitors who created the first chance when Williams' right cross was headed in by Mitrovic. Swansea continued to build on patiently from the back, with one very heavy pass culminating in a powerful 20-yard shot from Michael Obafemi that Marek Rodak parried over the bar.
From then on, Fulham really became dominant.