Coach: Andy Kelly. The former Hull KR and Wakefield forward has been involved in the Ireland set-up for more than eight years and stepped up to the head coach role in 2006.
He left his part-time role as Dewsbury coach earlier this year and will miss out on work in his day job as a self-employed kitchen fitter to travel to Australia.
Watch out for: Pat Richards. The Wigan star was in prolific point-scoring form this season, kicking 100 goals and crossing for 17 tries in Super League. A powerful runner, Richards also shores up the defence and will be a key player.
Richards helped Wigan get to within 80 minutes of the Grand Final this season
World Cup history: Made their World Cup debut in 2000, and performed admirably with the likes of Barrie McDermott, Steve Prescott, Chris Joynt and Brian Carney helping them win all three group games before losing 26-16 to England in the quarter-finals.
Chances: Ireland will struggle to match their achievements of 2000, and their chances were not helped by the late withdrawals of NRL duo Brett White and Shannon McDonnell. But with the anticipated support of many neutrals and the large community of Australians with Irish roots, Kelly's team could spring a surprise if they catch either of their pool opponents cold.
Did you know? Ireland flew on the same plane from the UK to Australia as the England players, but had to settle for standard seats while Tony Smith's men travelled in business class.
Coach: John Ackland. He is also assistant coach at New Zealand Warriors, who enjoyed a successful run in the recent NRL play-offs, falling just one game short of the Grand Final.
Watch out for: Ali Lauitiiti. A Grand Final winner with Leeds in 2007 and 2008, Lauitiiti possesses such wonderful off-loading skills that he can produce a pass from seemingly impossible positions. A seasoned international - for New Zealand.
Lauitiiti will play for Samoa but here he is in action for New Zealand
World Cup history: Samoa's only World Cup appearance came in 2000 when the team reached the last eight. They defeated New Zealand Maori and Scotland but lost to Ireland in the group stage. A quarter-final meeting with Australia brought their participation to an abrupt end.
Chances: Samoa have plenty of high-quality players but to qualify for the semis they must win their group. The match with Tonga promises to be a thrilling and decisive encounter.
Did you know? Samoa stand-off Ben Roberts is a first cousin of Everton midfielder Tim Cahill and says the Socceroos star was a useful league player in his youth.
Coach: Jim Dymock. The Canterbury Bulldogs assistant coach leads Tonga at the competition. He was a member of the Australia squad that won the 1995 World Cup and was a popular figure in Super League during a four-season spell with the London Broncos.
Watch out for: Epalahame Lauaki. The 24-year-old, who has New Zealand union international Sione as one of his nine brothers and sisters, is a force of nature on the field, playing with absolute commitment. His big hits are something best avoided.
Lauaki is often used off the bench for the New Zealand Warriors
World Cup history: Tonga made their debut in 1995, losing by just one point to New Zealand and drawing with Papua New Guinea. The Tongans lost to France and Papua New Guinea at the 2000 tournament but did register their only World Cup victory to date, a 66-18 win over South Africa.
Chances: Plenty of Tonga players have NRL experience. A lot will depend on their crunch game with Samoa but if they qualify from their group they could push for a place in the last four. Many expect them to have good tournament.
Did you know? Former Tonga captain Solomon Haumono quit the game in 2006 to become a professional heavyweight boxer and has won all his fights by knockout. His last ever game of rugby league ended with him being sent off after coming off the bench to get involved in a mass brawl on the pitch.