With the win, Lonard joins Gary Player, Jack Nicklaus, Greg Norman and Aaron Baddeley as the only five back-to-back winners over the last 50 years.
Stuart Appleby closed with an even-par 71 to take second place at minus-2. Third-round leader Rod Pampling struggled to a final-round, 4-over 75. He shared third place at 1-under-par 283 with Steven Bowditch, who closed with a 2-under 69.
Lonard carded three straight 71s to head to the final round at even-par. The Australian remained at even-par as he started his final round with 10 consecutive pars at The Australian Golf Club.
The 37-year-old moved to minus-1 when he drained a birdie try at the par-3 11th. Lonard came right back with a birdie at 12. However, he tripped to a bogey at the next.
Lonard fought back to birdie the 14th to get to minus-2. He made it two in a row when he dropped in a birdie try at No. 15. Lonard, who claimed his seventh international win, climbed to 4 under with a birdie at the 17th. He bogeyed the last, but held on for the win.
'I think this is probably bigger than last year. I think last year I came in thinking I could play a bit, this year I wasn't too sure,' Lonard said. 'To get my name on the trophy twice in a row is fantastic. It probably proves that it wasn't a fluke last year.'
Appleby hurt himself with bogies at the third, fourth and sixth. He got one stroke back with a birdie at No. 9. After a bogey at 10, Appleby birdied the 12th and 14th.
The Australian got within one of Lonard with a birdie at 16, but could only par the final two holes. Appleby had a chance to force a playoff, but missed a 10-foot birdie putt at the last.
Alistair Presnell climbed into a tie for fifth with a 3-under 68 in the final round. He finished at even-par 284 alongside first-round leader Kurt Barnes and left-hander Richard Green.
Robert Allenby, Gavin Coles, Rodger Davis, Martin Doyle and Paul Gow shared eighth place at 1-over-par 285.