A young Reds XI with plenty of changes endured a steep learning curve in the first 45 minutes as the Swans looked like their old selves; playing good football and scoring some great goals.
André Ayew opened the scoring with a header on 20 minutes, while Jack Cork followed with a lovely curling effort from the edge of the box before half time.
Christian Benteke did give Liverpool a lifeline off the bench in the second half, but Ayew restored Swansea's two-goal cushion less than three minutes later to wrap up the win.
A red card for Brad Smith after two needless bookings compounded Jürgen Klopp's misery, while the Swans can get excited about another season of Premier League football.
Sleepy Reds punished by sharp Swans
Liverpool brought a lot of emotion to South Wales this afternoon, and the pre-match routine saw Swansea play their part in celebrating the justice finally given to the 96 who were killed at Hillsborough 27 years ago.
However, whether the occasion affected the visitors, or whether it was down to the mass changes and hints of fatigue in between the two legs of their Europa League semi-final, the Reds were sloppy from the off and Swansea were keen to punish them.
A particularly poor few minutes from Klopp's side proved costly as Ayew would give the hosts the lead on the 20 minute mark. A lack of reaction would then see things turn from bad to worse, as Cork doubled this advantage shortly afterwards.
Their lead was well-deserved, capping off a strong period for the Swans which had seen numerous chances. Danny Ward came up with some big saves to deny both Ayew and Gylfi Sigurdsson, while Dejan Lovren produced a splendid block to thwart the former as well.
However, the Ghanaian would finally find the back of the net from the resulting corner, somehow beating Lovren in the air to head home and break the deadlock.
Swansea didn't stop there either. In fact, Francesco Guidolin's team could have wrapped the game up before the half hour mark, had they been more clinical.
A lovely exchange between Neil Taylor and Jefferson Montero saw the former cut back for Cork, but Ward produced another brilliant save to keep it at just 1-0 with Liverpool on the ropes.
Jordi Amat missed a sitter less than a minute later, his free header sailing well over the mark from four yards, while Montero too forced a good save out of the Reds' young goalkeeper.
All the missed chances were forgotten on 33 minutes though as some individual brilliance from Cork made it 2-0. Having wanted both the first and second balls more than any of his opposition, he was then given all the time and space to drive forward, pick his spot, and curl a shot past the helpless dive of Ward.
Too little too late
Klopp made changes at the break to try and influence the game, but the damage had already been done. Bar a good chance for Daniel Sturridge in the first half, which he dinked just wide of the mark, the Reds had been non-existent and found themselves two goals down.
The introduction of Lucas Leiva saw Pedro Chirivella removed after a difficult 45 minutes, with the manager wanting the Brazilian to help Liverpool assert themselves in midfield and get the ball moving around.
They did this immediately upon his arrival on the field of play, but there was little in the way of attacking flair to supply Sturridge and the other half time change, Christian Benteke, with chances to get the Reds back into the match.
The latter did head home to halve the deficit just past the hour, but that just woke the Swans up - who had been sloppy since the break - instead of rejuvenating the visitors as they restored their two goal lead through Ayew's second of the day.
Montero created this one but Liverpool's woeful defending played a huge part too, allowing the forward to get hold of the ball and steer home his brace less than three minutes after Benteke had scored.
Swansea could have added to the scoreline before the day was out, with Angel Rangel smashing a powerful half volley into the sidenetting after a second yellow for Smith saw the Reds reduced to 10.
However, it was the first half where the damage was done, and Klopp's side could not recover from the shock dealt to them by Guidolin's men.