This violet is an Australian native plant, or more accurately put, endemic to Australia. According to Mangroves to Mountains one of our field guides here, it is a tufted, herbaceous plant found in paperbark wetlands and mountains. Leaves to 20 cms, flowers to 20 mm spring and summer.
Though you could hardly call May spring! We haven't even had the shortest day of the year yet.
What allowed this species to spread, is its interesting ability to set fruit without first flowering! The plant develops seedcases at any time of the year, such as in the lower right hand corner of the pic just above the flower bud, that has split open and thrown the hard little seeds quite a distance.
This violet is host plant for an almost/probably extinct butterfly, the Fritillary, that I don't expect to see in my yard. Last sighting was about 30 years ago somewhere in Queensland.