Vicente del Bosque's men swept aside the Socceroos to secure third place in Group B, with the team's elimination already having been assured.
Vicente Del Bosque's men headed into their final group fixture knowing they could no longer reach the knockout stages following defeats to the Netherlands and Chile.
However, goals from David Villa, on his last international appearance, Fernando Torres and substitute Juan Mata ensured Spain at least signed off from the competition with victory, and avoided finishing bottom of Group B.
Spain's famous tiki-taka style has been derided in some quarters following the team's elimination, while there is also doubt over the future of Del Bosque.
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The defending champion was far from its fluent best on this occasion, but still did enough to earn an ultimately comfortable win.
After a slow opening, Spain turned up the tempo and Villa broke the deadlock nine minutes before the break with an improvised flick from close range, giving Australian fans a timely reminder of his talent ahead of his upcoming loan spell in the A-League with Melbourne City.
The impressive Andres Iniesta, collecting his 100th cap, then set up Torres for a second in the 69th minute, before Mata - Villa's replacement - rounded off the scoring late on.
Spain will still leave Brazil knowing it has much to ponder, while Australia can move forward with optimism after drawing plaudits for its plucky performances throughout the tournament.
Villa, Torres and goalkeeper Pepe Reina were handed starts in a much-changed Spain lineup, with the much-maligned Iker Casillas and Diego Costa among those dropping to the bench.
Australia showed more attacking vibrancy during a tepid opening, yet it was Spain which fashioned the first chance of note in the 20th minute.
Iniesta worked space on the right and showed great vision to pick out Villa at the back post, only for the forward to lash his volley wide.
Spain began to up the ante thereafter and Iniesta's clever backheel sent Jordi Alba free, but the fullback shot straight at Mat Ryan.
The lively Villa then showed neat trickery to bamboozle Mile Jedinak and fired a teasing cross along the six-yard box that neither Koke nor Torres could connect with.
However, Australia's resistance was broken in the 36th minute.
Iniesta's probing through ball caught Jason Davidson flat-footed and Juanfran got to the right byline before pulling back for Villa, who provided an ingenious close-range flick from behind his standing leg.
Spain struggled to rediscover a high tempo after the break, with several misplaced passes curtailing promising attacks.
The biggest round of applause for the second half was reserved for Villa, who was replaced by Mata shortly before the hour mark, the 32-year-old shaking his head as he emotionally exited the pitch before burying his head in his hands on the substitutes bench.
Spain's control of possession provided a second with just under 20 minutes remaining.
Iniesta was once again the architect with a defense-splitting pass that Torres collected on the left of the box before calmly slotting right-footed into the far corner.
Further gloss was added to the scoreline in the closing stages when substitute Cesc Fabregas picked out Mata in the penalty area, and the Manchester United man slipped the ball under goalkeeper Ryan.