The win was set up by a powerful batting display by the Southern Stars, who peppered the boundary ropes on their way to a mammoth 186 for 1 - the joint 4th highest total in T20 internationals.
Openers Elyse Villani and Ellyse Perry led the way with a first wicket stand of 121 in just 85 balls.
Villani top scored with 80 from 53 balls, hitting 12 fours and a six as she latched on to anything remotely loose from the Irish attack.
She looked destined to reach her hundred, before playing on after inadvertently hitting the ball twice off the bowling of Elena Tice (1-24).
Perry - content to play the anchor role up to that juncture - accelerated in the final stages, as she and the impressive Grace Harris added 65 off the last 35 balls of the innings.
Perry hit 7 fours in her 55 not out, while Harris thumped 3 fours and 2 sixes on her way to an unbeaten 39 from just 21 balls.
The boundary count showed that Australia hit 22 fours and 3 sixes in a fine exhibition of batting.
The Irish reply got off to another poor start as Clare Shillington (0) fell in the first over, while skipper Isobel Joyce (0) was for the second successive day run out while backing up - short of her ground after Megan Schutt deflected a drive from her twin sister Cecelia.
Spinners Jess Jonassen (2-7) and Grace Harris (1-13) yet again got the Irish batters in a stranglehold which they found hard to break free from, as Ireland stuttered to 45 for 6 in the 13th over.
Kim Garth - who had a fantastic all-round series - top scored with an undefeated 30 from 35 balls (4 fours), sharing a stubborn 7th wicket stand of 37 with Lucy O'Reilly (14).
Ireland finished their innings on 87 for 7 - a victory margin of 99 runs.
Grace Harris was named Player of the Series - a superb achievement for a player who made her debut in the first game on Wednesday.
Australia extend their record winning sequence to 16 T20I's - they are next in action in the ongoing Ashes Series where they face England in 3 T20's over the next week.
The series has been a fantastic learning curve for the young Irish side, and will prove invaluable to them ahead of the T20 World Cup Qualifiers in Thailand later this year. That qualifying competition takes place from November 28- December 5, when the Irish Women will attempt to emulate the men's side and qualify for India next year.
IRELAND WOMEN V SOUTHERN STARS (AUSTRALIA) 3RD T20I
At Claremont Road,
AUSTRALIA WOMEN 186/1 (20 overs, Elyse Villani 80, Ellyse Perry 55* , Grace Harris 39*, Elena Tice 1-24)
IRELAND WOMEN 87/7 (20 overs, Kim Garth 30*, Lucy O'Reilly 14, Jess Jonassen 2-7, Grace Harris 1-13)
