Ainscough, 20, has spent the first month of the season on a dual registration contract with Widnes, scoring four tries in three games with the Vikings.
The England academy international scored 17 tries in 12 senior appearances for the Warriors last term, and moves to The Jungle on a one-month loan deal.
Tigers boss Terry Matterson told the club’s official website: “With Richard Owen ruled out and Kirk Dixon not quite ready to return, although he should be back in a couple of weeks, I felt that was important for us to bring someone in pretty quickly. Shaun is an exiting young player who did very well last season but Wigan have a fair bit of strength in his position which saw him placed on a dual contract with Widnes, but I’m very pleased that we have been able to bring him on-board. He is very quick and he has shown that he knows the way to the line and I expect him to make his debut in Saturday’s game against Hull KR.
“Initially Shaun will be with us for a month, and he cannot be recalled in that time, but there may be an opportunity for that to be extended if it suits all parties
“However part of the deal with Wigan is that he will not be able to play in our game against them on the 21 March, and were the loan to be extended, he will not be able to play in the Carnegie Challenge Cup as understandably Wigan do not wish him to be cup-tied. I would though like to thank the Warriors for allowing the loan deal to go through.”
Ainscough is seen to be a replacement for Richard Owen, who will miss the rest of the season after breaking his leg against Bradford last weekend.