The tournament had been due to take place in France next year but the world governing body was forced to reorganise the calendar after the organisers pulled out for financial reasons.
The 2025 men's tournament was initially to feature 16 teams but this has been streamlined to 10 for 2026 and eight each for the women's and wheelchair competitions.
The tournaments will take place in October and November 2026 with some matches being staged in Papua New Guinea.
"The condensed format at RLWC2026 will mean every single match is competitive, while the possibility of some games being played as double or triple headers represents great value for fans wanting to see the best rugby league talent on the planet," said IRL chair Troy Grant.
"The culture, diversity and competitiveness of the nations involved will capture the attention of global audiences and grow the game ever further."
Australia last hosted the World Cup in 2017 with the most recent edition held in England in 2022 after a 12-month postponement due to the Covid-19 pandemic.
