The veteran former Hibs, Burnley, Wolves and Sunderland forward returns to Scottish football for the first time since 2009, when he left Easter Road for Burnley, after his contract with Stoke City expired.
Capped 33 times by Scotland, the 35-year-old has been a stalwart in the English Premier League and Championship, with the exception of six months on loan at Marseille in France, and will add experience to United’s front line.
United sporting director Tony Asghar said: “I am delighted to secure Steven's signature. He is a player we have tracked for a while and to attract a player of his calibre and experience is exciting for the club.”
Fletcher is set to followed to Tannadice by Manchester United’s 21-year-old midfielder Dylan Levitt.
The Welshman spent a successful loan spell on Tayside last season and is poised to formalise a six-figure transfer and a two-year contract.