Where is the auto-brightness setting on iPhone 15 Pro?

Please follow this path,

iPhone > Settings > Accessibility > Display & Text Size > scroll down > Auto Brightness > turn on, if it is on momentarily turn off and then back on.

OzzyWise wrote:

That's the problem that it's not there

As Jeff pointed out, it IS there in accessibility settings on that phone.

You must leave it ON, but remember the auto brightness is plus or minus around your desired setting for normal use. If you set it in Control centre to a medium brightness while you're in a room it should adjust for darker rooms and lighter days but there is a maximum for daylight use. Using a phone in bright sunshine will eat the battery and overheat the phone/battery.

Have you looked in the accessibility settings, it is located over there rather than display and brightness.

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I cannot find any reason, nor any setting in screen time, which would omit this setting from an iPhone 15 on iOS 18. I suggest you contact Apple support.

What iOS version is your iPhone using? Did you purchase the iPhone new from Apple? What is the history of your iPhone? Is it used? If so, the screen may have been replaced with non Apple parts.

Here’s a screenshot of my wife’s 15 Pro showing the feature.

...and the bottom of that page?