The Ospreys' storming display set them up for an EDF Energy Cup final rematch with Leicester as they saw off Saracens in Cardiff.
Two tries from Wales Grand Slam hero Shane Williams took his 2008 Millennium Stadium tally to seven in four games.
Gavin Henson and replacement Filo Tiatia added further tries after the Welsh region led 8-0 at the interval, while James Hook kicked 10 points.
Saracens tried to attack their blitz defence but could not make any headway.
English side's lone riposte was a penalty from Glen Jackson early in the second half, and they will take little confidence into their Heineken Cup quarter-final date with the Ospreys on 6 April.
The Ospreys dominated the opening minutes and were twice denied tries, the first time when Williams' dazzling golden boots gave him away as he trod on the touchline a split second before touching down.
That third-minute incident was settled by the television match official, and four minutes later referee Wayne Barnes adjudged that a pass from scrum-half Mike Phillips that sent Jonathan Thomas over was forward.
If the Ospreys believed those moments were merely the prelude to more fortunate moments in the opening quarter, they were wrong.
Instead, having been on the back foot from the first whistle, Saracens got themselves into some good territory and with full-back Brent Russell lively in attack, they lived up to coach Alan Gaffney's pre-match assertion that taking on the blitz defence would be a good policy.
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In the 28 minute, fly-half Hook kicking a penalty after Henson sent Thomas bursting away again only for Sarries flanker Don Barrell to kill the ball.
And just when it seemed Hook's kick would be the only points of the opening period, up popped Williams to hack ahead after Jackson's fumble under pressure from Henson.
This time the video verdict went the Ospreys' way as the diminutive wing touched down amid pressure from three chasing defenders.
However, Hook failed to convert, leaving Ryan Jones and his team with an 8-0 lead at the break.
Jackson made some amends four minutes after the break with his first kick at goal to keep the pressure on the Ospreys.
The Welsh team also had to come to terms with the arrival of Saracens scrum-half Jacob Rauluni - who played a key role in Fiji's memorable World Cup win over Wales - as a second-half replacement for skipper Neil De Kock.
Williams' dazzling footwork was again in evidence as he tried to lift his side, but it was fellow Wales star Henson who was to strike next.
Opposite number Andy Farrell left himself with far too much to do after Hook's pass gave Henson his chance, the Welshman handing off the former England centre on a 35m dash to the line.
Hook converted and kicked a 60th-minute penalty before back-row replacement Tiatia barged his way over as the Ospreys asserted their superiority, Hook again converting.
Lock Ian Evans played provider to Williams for his second try; the towering forward's delicate kick giving the smallest player on the field the simple task of gathering and running in unopposed.
But Henson took the man-of-the-match award for his outstanding efforts in attack and defence.
Ospreys: Byrne (Marshall, 45-48), Vaughton, Parker, Henson (Bishop, 72), Williams, Hook (Biggar, 78), Phillips (Marshall, 69); James (D Jones, 61), Hibbard (Bennett, 61), Adam Jones, Wyn Jones, Evans (Bateman, 73), Thomas (Tiatia, 61), Holah, Ryan Jones (capt).
Saracens: Russell, Haughton, Leonelli (Sorrell, 68), Farrell, Scarbrough, Jackson, De Kock (capt; Rauluni, 40); Lloyd (Yates, 71), Ongaro (Kyriacou, 59), Visagie, Jack (Ryder, 45), Vyvyan, Chesney (Gustard, 59), Barrell, Skirving.
Referee: Wayne Barnes (England)
Att: 41,018