Louis van Gaal confirmed on Tuesday evening that the 28-year-old forward, who has been at Old Trafford since 2004, would succeed Nemanja Vidic as United's skipper, with Darren Fletcher his vice captain.
"It is a huge honour for me – and for my family – to be named captain of this great club. It is a role I will perform with great pride," Rooney told the club's official website.
"Team spirit has always been very high in our dressing room and I am very grateful to the manager for the faith he has shown in me. I look forward to leading the team out on Saturday at our first match of the new season."
England international striker Rooney is United's third leading goalscorer of all time, having netted 216 goals in 442 appearances since joining the Red Devils from Everton as a teenager in 2004.