The 19-year-old will gain senior experience with the South Wales club, who currently sit 19th in the table under manager Graham Coughlan.
McNeill was an important member of United’s FA Youth Cup-winning side last season, with the Droylsden-born striker scoring five times across six starts in the competition for the young Reds, including twice in the semi-final victory over Wolves at Old Trafford.
He became the first Academy player to make a senior debut under Erik ten Hag in September 2022, replacing Tyrell Malacia for the closing stages of the 1-0 Europa League defeat to Real Sociedad at Old Trafford.