Australia (22) 55
Giteau scored a brace and kicked 17 points for Australia
Tries: Giteau (2), Mitchell (3), Ashley-Cooper, Hoiles
Cons: Giteau (4)
Pens: Giteau (3)
Fiji (5) 12
Tries: Neivua, Ratuva
Australia romped to a comfortable 55-12 victory over a second-string Fiji in the Pool B clash in Montpellier.
The Wallabies ran in seven tries to secure top spot in the group, setting up a likely quarter-final against either England or Tonga in Marseille.
Drew Mitchell scored a hat-trick, while Matt Giteau (2), Adam Ashley-Cooper and Stephen Hoiles also crossed.
Fiji scored tries from Isoa Neivua and Aca Ratuva but the Wallabies were in training mode ahead of bigger tests.
"It was a little bit scrappy in the first half, but we showed we are able to defend well at times," said man-of-the-match Giteau, who also kicked 17 points and won his 50th cap.
"Fiji defended well and put us under pressure. Hopefully we will have a good performance against Canada and get ready for the quarter-finals."
The Fijians, who were resting a host of top players, can still qualify for the knock-out stages if they beat Wales in the crunch match Nantes on 29 September.
"We thought we had a few chances at end of first half to chase the score and I was pleased with the younger players coming through, knowing that we've got a tougher game against Wales next week," said Fiji coach Ilie Tabua.
Australia took their time to unlock the Fiji defence and had to wait until 16 minutes for the first try after Wycliff Palu and Lote Tuqiri combined to put in Giteau.
The Wallabies went close soon after when George Gregan, equalling Will Carling's record of 59 caps as captain, was foiled yards from the line after Rocky Elsom's break, but Fiji, to their credit, held off the next Australia score until the half hour mark.
Full-back Chris Latham slipped a cute grubber kick through for winger Mitchell to gather and five minutes later Giteau added a second when he sneaked through following sustained Australian pressure.
The Wallabies were cruising but right on the whistle, a textbook Fijian passing move down the three-quarters picked out left wing Neiuva, who outmuscled five Australian defenders to crash over.
After the break, the hard-headed Australians spurned the chance to probe the corner with a penalty and took three more points through Giteau before Berrick Barnes added a drop-goal for good measure.
Fiji, though, were not prepared to go through the motions as understudies and a dazzling break from replacement Mosese Raulini fed open-side Ratuva for his side's second try.
The clinical Wallabies edged ahead again when Giteau slotted another penalty before conjuring a pass for Ashley-Cooper to slice over from close range.
But the game lost its shape for a while following a host of substitutes until Fiji went close with a promising break, only for Australia to surge upfield and score at the other end through Mitchell.
A male streaker 10 minutes from the end drew the biggest cheer of the day but Australia were not ready to start partying and ran in further scores from Hoiles and Mitchell.
Australia: Latham, Mitchell, Ashley-Cooper, Giteau, Tuqiri, Barnes, Gregan (captain); Dunning, Moore, Shepherdson, Chisholm, Vickerman, Elsom, Waugh, Palu.
Replacements: Freier, Holmes, McMeniman, Hoiles, Cordingley, Staniforth, Huxley.
Fiji: Ligairi; Delasau, Kunavore, Bai (capt), Neivua; Luveniyali, Daunivucu; Yalayalatabua, Sauturaga, Qiodravu, Domolailai, Rawaqa, Talei, Ratuva, Qovu.
Replacements: Gadolo, Railomo, Lewaravu, Koyamaibole, Rauluni, Lovobalavu, Rabeni.