Australia will head to next year's World Baseball Classic after beating South Africa 12-5 in the final of the four-nation qualifying tournament in Sydney.

Manager Jon Deeble's Southern Thunder scored six runs in the eighth inning - helped by a two-run throwing error on a bunt and a bases-loaded walk - to clinch victory in a game where the lead changed hands four times.

They will now join 16 other nations, including powerhouses Japan, United States and Cuba, at the WBC in March next year at a venue to be announced next month.

Mitch Dening and Trent Oeltjen hit run-scoring singles in the bottom of the seventh inning to break a 4-4 tie and give Australia a 6-4 lead.

Earlier South African catcher Kyle Botha's three-run homer in the top of sixth off Australian starter Travis Blackley had put South Africa up 4-3 but Australia, who outhit South Africa 17-7, tied it in the sixth on Trent D'Antonio's run-scoring double.

South Africa shortstop Gift Ngoepe led off the game with a long homer to left field off Blackley. But the Australians tied it in the bottom of the first on Oeltjen's RBI double off South Africa starter Kyle Gaddin.

Australia's second baseman Brad Harman and catcher Allan de San Miguel hit consecutive solo home runs in the bottom of the fifth, both off South Africa reliever Carl Michaels, to give Australia a short-lived two-run lead.

The Thunder were forced to qualify for the 2017 WBC tournament after leaving the last event winless.

Sunday's win followed Australian victories over the Philippines (11-1) and South Africa (4-1) earlier in the four-team tournament.

New Zealand lost to South Africa on Saturday.