The striker's contract at Manchester United expired in the summer and he has agreed terms with the Hillsborough outfit, who finished last term strongly under manager Danny Rohl.
It is an exciting move for the 20-year-old, who has linked up with the Owls at St George's Park, ahead of their pre-season campaign.
McNeill made his senior debut when Erik ten Hag brought him on as a substitute for Tyrell Malacia in the Europa League tie against Real Sociedad, at Old Trafford in September 2022.
Loan spells at Newport County and Stevenage have since furthered his education, and he regularly found the net in the Under-18 Premier League and Premier League 2, during his time in the Academy.