Player of the match Beth Mooney's unbeaten 53-ball 74 did most to put the pressure on the South Africans in their first-ever World Cup final appearance on Sunday as the Australians, opting to bat, amassed 6-156 at Newlands.
Then Lanning's team bowled and fielded with clinical efficiency to largely always stay in control, as they ended up restricting the Proteas to 6-137 to lift the T20 global title for the third time in a row and the sixth time in the last seven editions.
Player of the Tournament Ashleigh Gardner delivered the stand-out all-round performance on the balmy afternoon in front of a sell-out crowd of 13,000 to hand Lanning a memorable win in her 100th T20I as captain.
Gardner first helped propel Australia with her 21-ball 29 and then defended 26 off the game's final over to finish with 4-0-20-1 and ensure her side completed a three-peat in 20-over World Cups.
Among a fine combined effort from the Australian bowlers, Megan Schutt, Darcie Brown and Jess Jonassen also each took a key wicket as the Australians won a 13th world title in all in white-ball cricket.
Australia didn't notch up the victory at a canter, though. Laura Wolvaardt's 48-ball 61 and Shabnim Ismail's 4-1-26-2 inspired romantic hopes of an historic win for the first-time World Cup finalists South Africa.
Opener Wolvaardt had put the hosts within 48 runs of a win with her third straight fifty that anchored a 35-ball 55 partnership with Chloe Tryon.
But Schutt trapped Wolvaardt lbw in 17th over, leaving too much to do for Tryon, who fell for 25 off 23.
Earlier, Mooney's quickfire 15-ball 33 stand with No.6 Ellyse Perry (seven off 5 balls) ensured the defending champions scored 46 in the death overs.
The left-handed opener Mooney's clutch innings, reminiscent of her match-winning fifties in the finals of the 2020 T20 World Cup, the 2022 ODI World Cup and the Commonwealth Games final, again proved indispensable.
But, at one point, she was going so slowly, she admitted: "I actually asked one of the girls who ran out if she could ask Shell (head coach Shelley Nitschke) if she wants to retire me because I was hitting it that bad!
"That didn't quite make it to Shell ... but it just goes to show if you hang in there long enough and get the pace of the wicket…
"I probably didn't have a great plan through the middle there, stepping across and trying to hit it too square but once I stayed a bit still and hit a bit straighter, it wasn't too bad."
The Australian innings ended with a double-wicket 20th over from Ismail, who became the leading wicket-taker in women's T20 World Cup history with her 42nd strike in the tournament.
Gardner, promoted to Lanning's usual No.3 slot, had marshalled Australia from 1-36 in the powerplay after Alyssa Healy had been dismissed for a 20-ball 18 to double that run tally by the halfway mark.
Gardner's 41-ball 46-run second-wicket stand with Mooney, broke upon the introduction of Tryon as the 25-year-old holed out to long-off.
Tryon then took a superb catch at deep midwicket off a Lanning pull to reduce the opposition 4-122 with 17 balls left in the innings.
Australia amassed 34 off those deliveries. Mooney, who brought up her second successive half-century of this World Cup, off 44 balls, alone made 25 in that tally.
"People are looking out at us for what we do and how we go about it, so certainly it won't last forever," Mooney said of their title-winning spree.
"But we'll enjoy it for as long as we can and, hopefully, we can keep piling up those trophies and enjoying what's great."
