Hansen, 27, is the longest serving member of coach Matt Parish’s team, having first joined up with the squad back in 2007.
Parish said: “Harrison has been outstanding since day one with his attitude and leadership at training and in camp. I have no doubt he will inspire the boys to represent their proud nation of Samoa with the honour the Toa jersey commands.”
The Auckland-born back-rower came through the academy at Wigan, and has gone on to make more than 235 appearances for the Warriors.
Hansen said: “It’s a huge honour to represent my country of Samoa and my family. I thank Rugby League Samoa for this incredible opportunity. I look forward to working with this great team and having a strong and successful World Cup.”