Jonathan Rea was edged into second spot by double winner Marco Melandri in a thrilling race two of the opening World Superbike round at Phillip Island.
Three-time champion Rea, 31, took the lead on the final lap but the Italian passed him on the final straight to take his second victory of the weekend.
Ducati rider Melandri won by 0.021 seconds, with Spain's Xavi Fores third.
Melandri leads the series on 50 points, 17 ahead of England's Tom Sykes, who is two ahead of Kawasaki team-mate Rea.
Rea, who finished fifth in race one on Saturday, led the field after Eugene Laverty crashed out of a strong lead having set the fastest lap of the first half of the race.
Laverty ended up in the gravel but managed to get going again to finish 15th, two laps down on the winner.
Nine riders were duelling at the front before being forced to pit for a mandatory tyre change.
Fores, Rea and Yamaha-mounted Michael van der Mark were the first to pit for tyres, leaving Welshman Chaz Davies and Melandri at the front, with Sykes up to third.
Davies led the remaining top riders into the pits one lap later but crashed out of contention on his re-start lap.
Rea subsequently set the fastest lap of the race but Melandri bettered that soon after with a new lap record as he overtook Sykes and made up ground on Rea with relative ease.
Rea, a double winner at the Australian round in 2016 and 2017, pounced on Fores with three laps to go and Melandri followed suit, with Sykes closing in all the way.
Melandri passed Rea over the line on the penultimate lap, only for the Northern Irishman to hit the front again, but the Ducati rider was able to make the decisive pass on the closing straight.
Sykes finished fourth, with English riders Alex Lowes and Leon Camier completing the top six.
Rea is aiming to equal Carl Fogarty's record of four titles - although the Englishman's series successes did not all come in consecutive seasons.
The next round of the series will be staged in Thailand from 23-25 March.
|2018 WSB Riders' Championship|
|Marco Melandri (Ita)||Ducati||50 pts|
|Tom Sykes (Gbr)||Kawasaki||33|
|Jonathan Rea (Gbr)||Kawasaki||31|
|Xavi Fores (Sp)||Ducati||29|
|Alex Lowes (Gbr)||Yamaha||21|
|Leon Camier (Gbr)||Honda||19|