But if it had been a week or two later it would have been usurped by Pirates of the Caribbean: Dead Man's Chest.
Potter made $27.4m (A$35.7m) for Roadshow - Pirates, as of August 16 was up to $26.8m (A$34.95m) for BVI.
BVI was also the distributor with the most films grossing in excess of A$10m ($7.7m). Roadshow handles Warner Bros product in Australia.
Roadshow also handled the Australian winner, Wolf Creek, which took $4.7m (A$6.1m).
UIP was behind New Zealand's hit of the year, King Kong, which grossed $5.8m (NZ$9m). Sony distributed the foreign language winner Kung Fu Hustle, which grossed $1.5m in Australia.