The Canaries' relegation back to the Championship has already been confirmed and their miserable campaign hit another low on Sunday, as they were hammered 4-0 at home by West Ham United.
Williams has been one of the few relatively successful performers at Carrow Road this season, but could be in trouble with the club after the controversial social media post.
The 21-year-old uploaded a picture of himself displaying his middle finger, along with the caption:
“What a beautiful day. Easy up Norwich City”.
Williams posted another picture shortly after of his dog, and wrote:
“For the people that followed me, he's always awake”
The Mirror has suggested that the player was followed home by Norwich City supporters following the damaging home defeat.
Williams left Manchester United last summer on a season-long loan due to the left-back falling down the pecking order behind Luke Shaw and Alex Telles, and has since made himself a first-choice member of Dean Smith's starting XI.
The England U21 international has played 29 appearances during his spell in Norfolk, but has been unable to prevent his temporary side suffering a Premier League record 6th relegation this term.
Norwich supporters are clearly unhappy with how the club is being run, with around 200 people taking part in a protest against the board.
Williams claims there is "no point" of going back to Manchester United if he isn't going to play
The full-back made 36 appearances in his breakout season at the club last year, but in March he told The Mail that he wanted to prove he was a Premier League player and wasn't going to do that as a third choice at his parent club.
When asked about his future at the Red Devils, Williams later said:
"I'm playing games now and I love it. I can't wait for the weekend so I can get to the stadium. There would be no point in me going back to United and just sitting on the bench."
"I want to play and feel I'm better equipped for the Premier League after this experience. Whether it's at United or somewhere else, we'll deal with that in the summer. But I've got a job to do here at Norwich."
Upon his return, Williams will be desperate to show off what he can do to incoming manager Erik ten Hag, who will take the reins at Manchester United next season.