If you were just searching on how to download Fortnite on iPhone, you have landed on the right page.
Download Fortnite on iPhone
If you searched on App Store to download Fortnite and did not find the game, you aren’t alone. The reason is that developers of the game “Epic Games, Inc.” haven’t made the game available for iOS devices yet.

When visiting the download page on their website on my iPhone 12 mini, a message was displayed stating “Sorry, downloads are not available on iOS devices.”

Therefore, anyone with an iPhone or iPad won’t be able to play the game on their device. That being said, the game can only be played on a Mac device, Windows computer or on an Android device.
It’s unclear when the game would be available for iOS devices. Therefore, if you really need to play Fortnite, you might as well need to get a new suitable device for it. After all, it’s one of the best games to play.