Chapman, 24, who was a member of England's under-20 World Cup winning squad, has signed a two-year deal with the Bantams.
The Hartlepool-born player recently left Blackburn Rovers, having spent loan spells in League One sides Burton Albion and Shrewsbury Town in the previous two seasons.
The Teessider said: “I am delighted to be here. It has been quite a while in the pipeline but as soon as I came here, looked around and spoke to the manager, I knew I wanted to make this my home for the next two years.
“The gaffer and who he is drew me immediately, and when I spoke to him about his ambitions for the club, it was something I wanted to jump on board with.
“I am an exciting player who is quick and likes to take defenders on. I want to get supporters off their seats and entice them to chant my name.
“I am really excited for the start of the season and hopefully helping take this club back up the leagues to where it belongs.”
Bantams boss Mark Hughes added: “Harry is a player we are delighted to be bringing to the club, and is one we have had our eyes on for a number of weeks.
“He arrives with plenty of talent and a lot of experience at what is still a relatively young age, both in the football league and on the international scene.
“Harry is an exciting player who likes to entertain and get supporters on the edge of their seats, which I am sure you are very much looking forward to.
“He has the ability to play in a number of different positions and is at an important stage of his career where he has the opportunity to develop further and help us achieve our goals."