England beat Australia by three runs
England: 259-8 (50/50 overs. Beaumont 49, Brunt 45*, Gunn 39, Taylor 35; Villani 3-42, Beams 2-44)
Australia: 256-8 (50/50 overs. Perry 70, Lanning 40, Mooney 31; Hartley 2-31, Brunt 2-42, Gunn 2-54)
Katherine Brunt led the way as England recorded a first Women's World Cup victory over Australia since 1993 in a dramatic finale at Bristol.
Brunt blasted an unbeaten 45 in a seventh-wicket partnership of 85 with Jenny Gunn as her side set the defending champions 260 to win, and then took two for 42 and held on to a crucial catch in the final over to help England edge home by just three runs.
England edged themselves to the top of the group as a result, but Brunt was taking nothing for granted.
She told Sky Sports: "It's always nice to get one up on the Aussies, but this is just one game, there are a fair few more to come.
"Obviously that's the first one they've lost and they're doing well, so never count them out."
Having lost opener Lauren Winfield for one with the score on just six and then wicketkeeper Sarah Taylor and skipper Heather Knight having added 50 more, England found themselves rebuilding early on.
Tammy Beaumont and Natalie Sciver put together a partnership of 46 before the latter picked out Australia captain Meg Lanning at mid-off with Beaumont and Danielle Wyatt adding 54 before the opener finally fell one short of a half-century.
But it was bowlers Brunt and Gunn who added impetus at the end with Brunt's 45 coming off just 43 balls and Gunn making 39 before being stumped off Elyse Villani to help their side to 259 for eight from 50 overs.
Villani led the way for Australia with a return of three for 42 from five overs.
Her side's reply started in confident fashion as openers Beth Mooney and Nicole Bolton made it to 56 before the former fell to Alex Hartley for 31, and Bolton soon followed for 26 with the score on 72.
The situation was starting to look ominous as Ellyse Perry and Lanning eased them to 129 when the skipper was bowled by Hartley for 40 as she charged down the wicket.
Villani, dropped by Anya Shrubsole at mid-on off Hartley on two and then spared on review having been given out leg-before off Shrubsole, finally gave the bowler her first wicket when she holed out to Gunn to leave the score on 173 for four.
Sciver dropped Perry in the deep off Danielle Hazell in the 46th over, but after Brunt had bowled Alex Blackwell for 21 with the first ball of the next, redeemed herself by hanging on to Perry's skier on the rope to hand Brunt a second wicket in five deliveries with the Australian going for 70.
New arrival Ashleigh Gardner smashed Hazell for six as the first four balls of her penultimate over went for 15, but the bowler fought back to trap Alyssa Healy lbw for 14 off the fifth.
Needing 16 off the final over, Australia fell just short as Brunt took a priceless catch on the boundary to hand Gunn a second wicket and although a Sciver misfield meant a six from the final ball would have won it, Jess Jonassen was unable to oblige.
Lanning said: "It was a very close finish in the end, but England were just too good today."