The Netherlands striker, who spent the first part of the season on loan from Burnley to Turkish side Besiktas, has been allocated the no.27 shirt.
Wout was among the spectators at Old Trafford on Saturday, as Erik ten Hag's side triumphed 2-1 against Manchester City in a thrilling derby.
It remains to be seen whether the 30-year-old will make his Reds debut on Wednesday, when we travel to Crystal Palace in the Premier League, but the manager could give an update on that topic ahead of the trip to Selhurst Park.
Weghorst has never worn no.