After decades of futility, the Adelaide Giants suddenly have the making of an Australian Baseball League dynasty.

The Giants successfully defended their title on Sunday night to claim the Claxton Shield, coming from a game down to beat the Perth Heat 3-1 and win the championships series two games to one.

The first two games of the championship series are being hailed as Australian baseball classics, with Perth winning the opener at home 4-3 in a 13-inning marathon that lasted more than four hours.

The two teams had a 5am flight on Saturday morning to Adelaide for game two that night, where the Giants came from behind twice to win 6-3 and force the decider.

The Giants were a foundation member of the ABL when it originally started in 1989, but never won a title before the league was disbanded in 1999.

When the league restarted in 2010, Adelaide were rebranded originally as the Bite, but had the same fortune at the pointy end of each season.

They were runners-up four times in the new league until last season's breakthrough title.

The Giants were the dominant team through the ABL regular season.

On Sunday night, scores were tied at one-all until the bottom of the eighth inning, when Giants right fielder Briley Knight doubled with two out to score two runs.

Relief pitcher Todd Van Steensel then closed out the ninth inning to seal the win.

He was named the championship series most valuable player, pitching three scoreless innings across the three games with three hits and five strikeouts.