It was a five goals to none third term that set up the win for the Dogs after a tight first half, with the Swans eventually falling 16.10 (106) to 9.15 (69).
The Bulldogs will now face reigning premiers Geelong in a preliminary final next weekend.
Solid performances from Brett Kirk, Barry Hall and Paul Bevan weren't enough to save the Swans, with the Dogs applying vice-like pressure across the field and locking the Swans up with 66 tackles to 54.
A lack of scoring potency hurt the harbourside team, with Hall top-scoring with four goals and just five others booting majors.
By contrast the Dogs had 11 individual goal-scorers.
Darren Jolly was effective with 13 hit-outs and two tackles, while the Swans' defenders, particularly Bevan, Tadhg Kennelly and Lewis Roberts-Thomson, did well to rebound the Dogs' attacks in the opening half.
Once the floodgates opened for Rodney Eade's men in third quarter, the Swans were unable to stem the flow as the home side found room to run into attack.
Bulldogs Matthew Boyd and Lindsay Gilbee were terrific, as was tagger Dale Morris, while Josh Hill provided a spark up forward in the third term.
From the first bounce, the match was played at a cracking pace.
Brad Johnson and Jason Akermanis were felled in the second term – the former with concussion and the latter a split head – before both returned to see out the quarter.
At quarter time, the scores had been level twice, the lead had changed four times, and the difference was a point to the Swans.
Hall was playing well on Brian Lake, while the defence was holding up admirably.
In the second, the Swans twice got nine points clear, but missed a golden opportunity midway through when a bench mix-up saw a Dogs' shot on goal reversed.
Kennelly hit the post after being gifted a free and a 50m penalty when Tim Callan re-entered the field incorrectly.
Two late goals to the Dogs saw them hold a four-point half-time lead, with the biggest difference between the two sides the tackle count – the Bulldogs ruling with 38 to 26.
It was in the third quarter it started to go wrong for the Swans. The momentum fell the Dogs' way early after Hill goaled within three minutes, and that's where it remained for the rest of the term.
While the Bulldogs kicked away to a 32-point lead at the final change, the Swans were stagnant and couldn't find the big sticks, with Lake keeping Hall to four touches and Morris shutting Adam Goodes out of the game in the match-defining quarter.
Kirk upped his contribution and Luke Ablett moved to tag Boyd, and when Hall kicked the first goal of the last term many hoped for an unlikely comeback, but three quick goals to the Dogs sealed the contest.
Western Bulldogs 2.3 6.5 11.9 16.10 (106)
Sydney Swans 2.4 5.7 5.13 9.15 (69)
GOALS
Western Bulldogs: Murphy 3, Welsh 2, Hill 2, Eagleton 2, Higgins, Hahn, Lake, Griffen, Minson, Akermanis, Johnson
Sydney Swans: Hall 4, Roberts-Thomson, Jolly, Goodes, Crouch, Bevan
BEST
Western Bulldogs: Boyd, Gilbee, Morris, Griffen, Murphy, Lake, Hahn
Sydney Swans: Kirk, Bevan, Hall, Jolly, Kennelly, Roberts-Thomson
INJURIES
Western Bulldogs: Nil
Sydney Swans: Nil
Reports: Barry (Sydney Swans) reported by umpire Ryan for striking Higgins (Western Bulldogs) in the fourth quarter
Umpires: Vozzo, McBurney, Ryan
Official crowd: 42,731 at the MCG
