Former international Massimo Luongo, who made 45 appearances for the Socceroos, has been a key component of the Ipswich midfield.
Meanwhile, the Scottish-born Cam Burgess - whose family emigrated to Perth when he was 11 and who has played seven times for Australia - has been a defensive stalwart.
Both were in action as Ipswich beat Huddersfield 2-0 to finish runners-up behind champions Leicester on the final day of the regular season, sparking a joyful pitch invasion at Portman Road.
It is the second straight promotion for the team nicknamed the Tractor Boys, who have been revitalised since Kieran McKenna became manager in December 2021, when the club was in the third tier.
Leeds, whose American ownership group includes major-winning golfers Jordan Spieth and Justin Thomas, were the only team who could have prevented Ipswich from finishing second,
They needed to make up a three-point deficit on their rivals, but lost 2-1 at home to Southampton.
Since relegation from the top flight at the end of the 2001/02 season, Ipswich have struggled with financial issues and, in 2019, fell to the third tier for the first time since 1957.
Their recovery has been led by McKenna, a former Northern Ireland youth-team player who retired early because of injuries and preaches expansive, attacking football as a coach.
Leeds join Southampton, West Bromwich Albion and Norwich in the play-offs for the third promotion spot.
The Yorkshire club will play Norwich over two legs, while Southampton take on West Brom to determine which two sides contest the play-off final at Wembley Stadium on May 26.
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