Yapp has included 10 World Cup debutantes for the Salford clash on Saturday (9pm AEST), while Ash Marsters has been named on the bench in her third tournament.
NSW Waratahs rising star Halse, who has 11 caps, is set to become the youngest Australian woman to ever play at the global showpiece.
Becoming the youngest debutante in either the men's or women's Test teams in 2024, the 18-year-old will eclipse the previous World Cup record set by Millie Boyle in 2017 (19 years, 82 days) when she takes the field.
Katalina Amosa will start at hooker while her older brother Brandon Paenga-Amosa is the reserve rake for the Wallabies, who will take on the Springboks in Cape Town a few hours later.
The pair are the third sister-brother combination to play Test rugby for Australia.
Kaitlan Leaney will become the 20th captain of the Wallaroos, joining back-rower Emily Chancellor in sharing the duties against Samoa.
The Wallaroos will be boosted by the return of prop Brianna Hoy, who will come off the bench for her first game since rupturing her ACL during a training session in Ireland last September.The Coffs Harbour product is one of five changes to the side that defeated Wales at North Sydney Oval earlier this month.Experienced pair, prop Asoiva Karpani and centre Cecilia Smith return to the starting line-up, Adiana Talakai is the back-up hooker while veteran outside back Lori Cramer also comes into the 23 as a utility on the bench.
Sevens superstar Charlotte Caslick was ruled out of the tournament following ankle surgery, while injured skipper Siokapesi Palu (foot) is with the squad but was unavailable for selection.
The Wallaroos have previously met Samoa once in a Test match for an 87-0 victory in 2010. More recently an Australia A side defeated Manusina 50-22 in Canberra.
Yapp said preparation had been smooth in their northern England base.
"We've had a good week settling into Manchester with everyone making us feel really welcomed and the players have hit the ground running at training," she said in a statement."We know Samoa will be a tough, physical side and we need to match it with them on Saturday."There are no second chances at a World Cup and for us it starts with a good performance in our first match and building from there."It's also fantastic to see Bri Hoy back in the team. We know how hard she has worked to make a return in time for the World Cup and she is deserving of her spot."We're also really pleased to be able to give co-captaincy to Kaitlan Leaney, who is growing as a leader in the team every day."The Women's Rugby World Cup will be the eighth campaign for the Wallaroos, with their best finish coming in 2010 when finishing third.
Following Samoa, the Wallaroos take on USA on August 31 and top-ranked tournament hosts England on September 6 to complete their pool matches.
WALLAROOS: Caitlyn Halse, Maya Stewart, Georgina Friedrichs, Cecilia Smith, Desiree Miller, Faitala Moleka, Samantha Wood, Tabua Tuinakauvadra, Emily Chancellor (co-capt), Piper Duck, Michaela Leonard, Kaitlan Leaney (co-capt), Asoiva Karpani, Katalina Amosa, Faliki Pohiva. Reserves: Adiana Talakai, Brianna Hoy, Bridie O'Gorman, Ashley Fernandez, Ashley Marsters, Layne Morgan, Tia Hinds, Lori Cramer.
