The 28-year-old England striker succeeds Nemanja Vidic after the Serbia defender left the club at the end of last season to join Inter Milan.
“For me it’s always very important the choice of captain,” said van Gaal in a club statement issued after United’s 2-1 friendly win against Valencia at Old Trafford on Tuesday.
“Wayne has shown a great attitude towards everything he does. I have been very impressed by his professionalism and his attitude to training and to my philosophy.
“He is a great inspiration to the younger members of the team and I believe he will put his heart and soul into his captaincy role.”