The addition of the 23-year-old number eight, who stands at 6ft 2in and weighs 17 stone, is a welcome boost for coach Richard Hill, who currently only has Kai Horstmann able to fill the roll at the back of the pack.
Hill told the club's official website: "Richard is a young player who will be experiencing club rugby outside of Samoa for the very first time.
"He has been on tour in Europe before, but this will be a big change of culture. We will initially give him time to settle in and acclimatise.
"This is a big opportunity for him and if he can make an impression and prove himself then we will look to contract him for even longer.
"Richard is a talent and was very highly recommended by Brian Lima, who knows a good player after featuring in five World Cups. He is firmly regarded as a really big prospect for Samoa and one we believe can make big strides at Warriors."
Muagututia, who made his Test debut against Japan last year, added: "This is a great opportunity for me and a new start. It is exciting to join the Warriors and to play in England. I will play hard and for the future and hope to make a good impression with the supporters."
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