Manager Gareth Southgate confirmed the news at a press conference earlier today.
Delph has 16 England caps, the first of which came back in 2014 against Norway.
The game against the USA, a friendly at Wembley, is in honour of the Wayne Rooney Foundation, with the DC United striker coming back from international retirement to make his 120th international appearance.
Southgate, who also confirmed that the captain's armband will pass to Rooney at some stage during the game, said: "Fabian is captain tomorrow night.
"You don’t give the England captaincy to somebody unless they really have the attributes that can carry it.
"Fabian was huge for the group in the summer and he was one of the reasons we were successful.
"The players are also very keen that Wayne wears the number 10 and we believe that is a fitting tribute.
"We have spoken about doing things our own way over the last two years and we have a lot of respect for our former players."
Delph said he was proud to be awarded the honour of leading his country.
He said: "When I first came into the England set-up, Wayne was captain, he welcomed me and put his arm around and made me feel at home. As soon as he comes on I will give him the armband back.
"We're going to be giving him a guard of honour it is going to be a huge night for Wayne and it is important we honour him for all of his achievements throughout his career.
"I'm fortunate enough to have thoroughly enjoyed played for England.
"Under Roy Hodgson I had a good spell and under Gareth it has been absolutely amazing and I can't wait to meet up and get my teeth into what the gaffer wants us to do."
Last season, Delph played 29 games in all competitions as City won the Premier League and Carabao Cup and was part of the England squad that reached the semi-finals of the World Cup in Russia this summer.
Everyone at City would like to congratulate Fabian on what is a richly deserved accolade.