How do I reinstall Safari on my iPhone?

The Safari app is not one of the apps that can be deleted but with iOS 14 it can be removed from the home screen. If you have iOS 14, go to the App Library (swipe left past your last home screen). From there you can touch and hold an app and slide it left back to the home screen.

If that is not the cause, try using Search to see if that will locate it: https://support.apple.com/en-us/HT201285

You can’t delete Safari from your iPhone, so it is on the iPhone somewhere. Try searching for it.

Safari can be disabled in Screen Time settings; if that’s a possibility check there.

Safari is included with iOS on your iPhone. Update iOS to receive the latest Safari version.