Woosnam triumphed his match over defending champion Lee Westwood in an early 10-and-9 routing at the Wentworth Club.
The Welshman and two-time champion of this event (87 and 90) began his domination early and never let up for a moment.
Woosnam won the first hole with a birdie and went on to win four more holes over his front nine alone, going 5-up.
He ended with an opening 18-hole score of 66 that saw him extend his lead over Westwood to 7-up. The only hole that Westwood won came at the par-4 11th, when Woosnam made a bogey.
Three more unanswered birdies over holes 19 through 26 saw Woosnam increase his lead to an incredible 10-up, and the match was ended at the 26th (par-4 9th), when both men scored pars.
The 43-year-old veteran is finding great success in his later years in the game. This week alone, he has beaten reigning U.S. Open champion Retief Goosen 4-and-3 in the first round, and Colin Montgomerie 4-and-3 in the quarterfinals.
While he has not won on the season, he has recorded three top-4s on the European Tour, including a tie for third at the British Open.
Ive been swinging well recently and thought that a win was just around the corner, claimed Woosnam. Maybe this will be it. Theres no reason why not if I play like today.
In the second match of the day, Harrington continued his strong form as well, ousting 2002 Ryder Cup captain Sam Torrance 4-and-3.
While Woosnam took control of his match from the beginning, Harrington got it going in the afternoon.
The Irishman was A/S with Torrance following the opening 18, but rattled off three birdies and an eagle over a five-hole stretch from the 19th to the 23rd, creating a 4-up lead.
Torrance got two holes back with birdies at the 25th and 26th (par-4 7th and 8th) to cut his deficit to 2-down, but Harrington struck back not long after, winning two more holes and ending the match on the 33rd hole four ahead.
Like Woosnam, Harrington has been dominant in each of his matches thus far.
The 30-year-old has beaten Nick Faldo in a 9-and-8 opening-round route, and then Darren Clarke 5-and-4 in the quarters.
His win on Saturday puts him in a position much like Woosnam in another regard as well ' he is searching for his first win of the season.
Harringtons case is a bit more dramatic, however ' he has finished second on six occasions in his 17 events on the 2001 European schedule.
Click Here for Scores from Saturday's Semifinal Results at the Cisco World Match Play Championship.