The Dutch man is seen as a short term solution to their lack of in squad depth up front since Cristiano Ronaldo’s contract was terminated in November.
Wout Weghorst was on loan at Besiktas from Burnley till the end of the season but was opened to joining the Red Devils till the end of the season.
“I feel privileged to be joining Manchester United. I’ve played against the club in the past and it’s a fantastic feeling to now have the chance to pull on the famous red shirt,” Weghorst said.
“I’ve seen United’s progress under Erik ten Hag this season and can’t wait to start playing my part in pushing the team towards its aims.
“Whatever happens in the next few months, I can promise to give everything to the club for as long as I am here. I thank everyone who has played a part in getting me to this stage, and now I am looking forward to meeting my new team-mates and getting involved straight away.”
Weghorst has 13 G/A since joining Besiktas on loan he also has 19 international caps with the Hollands scoring 5 goals.
Manchester United football director John Murtough said: “Wout has a consistent goalscoring record across several European leagues, and his attributes will add a further dimension to our squad for the remainder of the season.
“We were also attracted by his strong personality and dedicated approach to football, which fits perfectly with the spirit that Erik is building within our squad.
“He has shown a huge desire to join Manchester United and be part of what we’re striving to achieve this season.”