The 25-year-old versatile player signed a five-and-a-half-year contract with an option to extend for a further year.
Fernandes claimed he was inspired to join United after watching Cristiano Ronaldo play for the club earlier.
This is what the talented Fernandes claimed.
January transfer window: Fernandes seals the biggest move in EPL
Fernandes has joined for a staggering £47 million but add-ons could increase the overall cost to £67.7 million.
His move is the biggest in the Premier League so far during the January transfer window which is set to shut tonight.
The mid-fielder follows the likes of Ronaldo, Nani and Marcos Rojo in joining United from Sporting.
He said he was delighted to join United.
Fernandes' love for United started after watching Ronaldo play
"My love of Manchester United really started when I used to watch Cristiano Ronaldo play and ever since then I have been a big fan of this great club," Fernandes said.
Ronaldo played for United from 2003 to 2009 and won a host of trophies under Sir Alex Ferguson.
He scored 118 goals in 292 matches for the club before switching to Real Madrid.
I have worked hard to get to this moment: Fernandes
Fernandes said it is an incredible feeling for him to play for the Red Devils.
"For me, to now play for Manchester United feels incredible. I have worked hard to get to this moment and I can promise the fans that I will give everything for the badge to help bring us more success and trophies," the mid-fielder claimed.
Fernandes was a success at Sporting
Fernandes joined Sporting for £7.2 million from Sampdoria in 2017.
He amassed 64 goals in 137 matches across competitions for Sporting and won the Portuguese Cup in 2018-19.
Fernandes was also named the Primeira Liga's Player of the Year in both 2017-18 and 2018-19 and has played 19 times for his country - winning the UEFA Nations League in 2019.
He will be a fantastic addition to our team: Solskjaer
Manchester United boss Ole Gunnar Solskjaer said Fernandes will be a fantastic addition to the side.
"Bruno's goals and assists stats speak for themselves. He will be a fantastic addition to our team and he will help us push on in the second part of the season. We have been tracking Bruno for many months and everyone here has been tremendously impressed," he said.