Sassuolo playmaker Volpato, 22, headlines Australia's 26-man squad along with 25-year-old uncapped striker Tete Yengi.
Skipper Mat Ryan and veteran Mathew Leckie head to a fourth World Cup, joining Tim Cahill and Mark Milligan in that rare group, while the squad features 17 players selected for their first.
Those include 18-year-old centre-back Lucas Herrington, star defenders Alessandro Circati and Jordy Bos and dynamic attackers Nestory Irankunda and Mohamed Toure.
But it was heartbreak for veteran forward Martin Boyle, defender Kye Rowles, forward Brandon Borrello and goalkeeper Joe Gauci, who were cut by coach Tony Popovic.
"A range of factors has gone into selecting this final World Cup squad," Popovic said in a statement.
"Some difficult decisions had to be made - that's the nature of major tournaments.
"But it's also a credit to all the players involved over the past few weeks who worked extremely hard during an extended and challenging pre-camp.
"I'd like to acknowledge the players who contributed to our direct World Cup qualification but are not part of this squad. Their contribution should not be forgotten."
The Socceroos play their final warm-up game against Switzerland on June 6 (June 7 AEST) in San Diego.
They then face Group D opponents Turkey in Vancouver on June 13 (June 14 AEST), the United States in Seattle six days later then Paraguay in Santa Clara on June 25 (June 26 AEST).
Sassuolo winger Volpato, 22, only arrived in camp on Saturday morning (local time) - too late to feature in that night's 1-0 loss to Mexico - after switching his allegiance.
Volpato knocked back Graham Arnold's pitch to join Australia's 2022 World Cup squad, then in March said he was waiting for a call-up from Italy's senior team, before his change of heart.
Yengi, younger brother of fellow Socceroo Kusini Yengi, was selected despite not playing against Mexico, having impressed at Japanese club Machida Zelvia, on loan from Scottish outfit Livingston.
Harry Souttar and Leckie were selected after overcoming horror injury runs to make their first Socceroos appearances since 2024 in the Mexico friendly.
Aziz Behich, Jackson Irvine and Milos Degenek reach their third World Cup.
Rowles, a starter in 2022, misses out as does Boyle - who was injured ahead of Qatar and again falls agonisingly short of playing at a World Cup.
Gauci started ahead of Ryan early in Popovic's tenure but fell out of favour.
Five A-League Men players were selected: Patrick Beach, Behich, Leckie, Paul Okon-Engstler - son of Socceroos assistant Paul Okon - and Nishan Velupillay.
Popovic will address the media on Sunday evening (Monday morning AEST).
SOCCEROOS WORLD CUP SQUAD
Goalkeepers: Patrick Beach*, Paul Izzo*, Mat Ryan
Defenders: Aziz Behich, Jordan Bos*, Cameron Burgess*, Alessandro Circati*, Milos Degenek, Jason Geria*, Lucas Herrington*, Jacob Italiano*, Harry Souttar, Kai Trewin*
Midfielders: Cameron Devlin, Jackson Irvine, Connor Metcalfe*, Mathew Leckie, Paul Okon-Engstler*, Aiden O'Neill*
Forwards: Ajdin Hrustic, Nestory Irankunda*, Awer Mabil, Mohamed Toure*, Nishan Velupillay*, Cristian Volpato*, Tete Yengi*
* First World Cup selection