The Portuguese midfielder is believed to have impressed club scouts in recent months and the Red Devils are ready to make their move.
Benfica are willing to sell Felix but will demand big money for the 19-year-old star.
Manchester United are on the lookout for reinforcements to help them try and challenge for major honours once more.
Even though interim boss Ole Gunnar Solskjaer has steadied the ship at Old Trafford since replacing the sacked Jose Mourinho in mid-December, there is lots of work still to be done.
A 2-0 home defeat to Paris Saint-Germain in the Champions League last-16 first-leg on Tuesday highlighted the gap that still remains between them and Europe’s elite.
According to Velox SportsTV, bringing in Felix is seen as a top priority for United.
An Old Trafford source told Velox SportsTV: “The club went to see Felix in action and it was all positive. He is seen as a real talent.
“He is definitely someone who is increasingly of interest. He is a clever playmaker and in a similar vein to Portugal legend Deco.
“He is definitely someone who is increasingly of interest”
Man Utd source
“The scouts saw him during the derby against Sporting Lisbon and he scored.
“There looks like there is going to be moves for him.”
Real Madrid and Bayern Munich have also been credited with interest in Felix.
The playmaker is being described by some in Portugal as “the next Deco”.
Benfica will try and tempt the midfielder into staying with them with a new contract offer, according to reports, but whether or not they could achieve that is unknown.
United signed Diogo Dalot from Portuguese side Porto last summer and they have previously signed Cristiano Ronaldo and Nani from the country.
Should United end up signing Felix for the fee being reported, he would become the club’s record signing.
That honour currently still stands at the £89m paid to bring back France international Paul Pogba from Juventus.