United boss David Moyes had pursued the Belgium international for much of the transfer window and finally got his man late on the last day.
A statement on Everton's official website confirmed: "Marouane Fellaini has moved to Manchester United for a £27.5m fee... Fellaini's exit ended a summer long period of speculation after the Belgium international emerged as one of former Everton manager David Moyes' prime targets for his new club."
Fellaini became Everton's club-record signing after arriving from Standard Liege for £15million in September 2008. He went on to make 177 appearances at Goodison Park, scoring 33 goals.
Originally a holding midfielder, Fellaini proved an attacking force for the Merseyside club under Moyes last season, scoring 11 times in 31 league games.
A bid for two Everton players from United - thought to be Fellaini and Leighton Baines - was rejected and labelled "derisory" by Everton in August, and while Baines does indeed appear set to stay on Merseyside, Fellaini has now finally made the switch to Old Trafford.
Meanwhile, United appear to have missed out on a deal for Athletic Bilbao midfielder Ander Herrera.
Reports had suggested that the Premier League champions were prepared to meet a €36 million buy-out clause in the attacking midfielder's contract at the Estadio San Mames, but a deal between United and the Spanish Football Federation - with whom the deal would have been concluded - remained unconfirmed as the deadline passed.
