Kingdom Hearts owned and produced by Square Enix. Some characters owned by Disney.

What do you get when you combine the worlds of Disney and Final Fantasy? Through some miracle, you get a successful gaming franchise like Kingdom Hearts. Typically focusing on Sora, wielder of a mysterious (and powerful) Keyblade, Kingdom Hearts is the story of a war against the Heartless, a breed of black-skinned creatures seeking to envelope the known universe in darkness. Sounds simple, gets really complex.

Kingdom Hearts features several non-canonical entries, which are only included under Release Order. It also includes a number of HD re-releases. Normally these would only be included under Release Order, however they all contain new material that foreshadows later releases in the series. You don't have to play the HD remakes to understand the story, if you have access to an earlier version of one of the games. (I recommend watching the extra content on YouTube.)

The one exception to the HD remakes listed above is Kingdom Hearts 0.2: Birth by Sleep - A Fragmentary Passage, which is part of Kingdom Hearts HD 2.8 Final Chapter Prologue. This is a new game only found in the HD remake, and it's long enough (though still not very long) that you should probably play the HD remake instead.

 In-Universe Chronological Order
Release Order