Fellaini will enter the final six months of his contract in January, and French newspaper Le10Sport reported he's on PSG's shortlist of potential recruits in defensive midfield (h/t MailOnline's Jaime Wright).
Wright wrote that Fellaini has already turned down the opportunity to extend his current £120,000-per-week United deal on the same terms and is presumably not at ease with his fringe status under manager Jose Mourinho.
Fellaini has started only four games across all competitions this season, but former Manchester City and England defender Danny Mills recently appeared on BBC 5 live Sport and suggested he can play to a higher level:
It seems surprising Ligue 1 leaders PSG would offer a four-year contract to a United fringe player who just turned 30 on Wednesday—he'd be 34 if he were to remain at the Parc des Princes for the entirety of that deal.
While his lack of involvement in the starting XI may suggest Fellaini isn't one of Mourinho's favoured stars, Goal recently jested otherwise and referenced some of the compliments aimed toward the towering middle man:
Fellaini was brought to Old Trafford by former Everton manager David Moyes after he took charge of the United helm in 2013, at which point he was much closer to a No. 10 than a defensive or anchoring midfielder.
The abundance of creative and attacking talents at United have led to him gravitating deeper in midfield since then, and it's precisely those kind of attributes PSG will be hoping to pick up on a free transfer next summer.
The French giants sold Blaise Matuidi to Juventus over the summer, while Grzegorz Krychowiak is on loan at West Bromwich Albion after a disappointing 2016-17 season and 35-year-old Thiago Motta could leave when his deal expires in June.
PSG aren't alone in their interest, however, and Emre Sarigul of Turkish-Football.com reported earlier in November that there is interest from the Super Lig and China also:
News of Fellaini's refusal to extend his United stay suggests a 2018 exit is likely, and he'll be free to sign a pre-contract agreement with any club outside the Premier League at the end of January.
There is a question as to whether he can expect to see his starting chances improve in the French capital, but if so, Fellaini's prospects could quickly turn around as he looks to swap one continental titan for another.