Australia skipper Meg Lanning says she never doubted her side would chase down a record target of 258 to beat Sri Lanka and seal a second successive win at the Women's Cricket World Cup.
Lanning scored an imperious 152 not out as Australia raced to 2-262 inside 44 overs to win by eight wickets.
However, her fine innings was overshadowed by a brilliant unbeaten 178 from Sri Lanka's Chamari Atapattu.
Atapattu was one of only three players in her side to reach double figures, but struck the highest-ever score by a female player against Australia in a record-breaking knock that included six sixes and 22 fours.
It was also the highest proportion of runs scored by an individual in a women's ODI.
"It was a very special innings from Atapattu," Lanning said.
"We tried all sorts of different things to slow her down and get her out but she was too good for us today.
"Some of those shots she played were incredible and well done to her. It was one of the great knocks."
Buoyed by the fireworks of their No.3 batswoman, Sri Lanka dismissed Australia opener Beth Mooney for a duck in the first over.
Nicole Bolton was lucky not to follow her back to the pavilion shortly after as wicketkeeper Prasadani Weerakkody dropped a simple catch when she was on five.
But it proved to be the only alarm for the world champions as Lanning underlined her status as the world's best batswoman with her 11th ODI ton after putting on 133 for the second wicket with Bolton (60).
After Bolton's dismissal she was joined at the crease by Elysse Perry, who scored 39 not out, with the skipper smashing a six to seal the win and bring up the biggest score of her international career.
"I thought we were good in patches with the bat and ball but it wasn't our best performance," she said.
"At the moment the wickets and the grounds are conducive to scoring runs and as soon as you get any width you feel you can free your hands.
"We were confident of chasing it down and although they got a few more than we would have liked, with our batting line-up and a good wicket we thought we could win.
"Once we set that base, Bolts and I, we knew we'd be able to chase it down."
Australia's bowlers shared the wickets between them with Perry, Kristen Beams and Bolton bagging two apiece.
Megan Schutt, Ash Gardner and Elyse Vilani each took a wicket.
New Zealand are Australia's next opponents on Sunday, again at Bristol.
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