The 38-year-old Sousa, a cultured midfielder who was part of Portugal's "golden generation" and was capped 51 times by his country, has signed a two-and-a-half-year contract.
"It is an honour to be part of this project," Sousa, whose club career included stints with Benfica, Juventus and Inter Milan, told QPR's website.
"I have always wanted to work for a big club and I am very excited about the opportunity to work for Queens Park Rangers."
Sousa will find himself just down the road from Luiz Felipe Scolari who quit as Portugal coach to join west London neighbours Chelsea this year. Sousa was the Brazilian's assistant for five years.
Sousa is the third new manager at QPR since Renault Formula One boss Flavio Briatore bought the club with a group of friends, including F1's billionaire supremo Bernie Ecclestone, in September 2007.
He succeeds Iain Dowie who was sacked 15 games after himself replacing Italian Luigi De Canio.
"I have been keeping track of his work for the last few months and he is the right man for our project," Briatore told the club's website.
"He has great experience after working with the Portuguese national team and he is part of the new generation of coaches. He has worked with some of the world's best players and we are excited about having him."
QPR are 10th in the Championship, three points behind the promotion playoff places.
