Here's the quickest thing to try first. Plug your Galaxy S26 Ultra into a wall outlet using a Samsung 60W Super Fast Charging 3.0 charger and cable if you have one. Let it charge, undisturbed, for at least 30 minutes.
If the screen stays black, press and hold the Volume Down button and the Side/Power button simultaneously for about 10 seconds. This is the force restart, and you should feel a vibration and see the Samsung logo when it works.
If the logo appears, you're back in business. If it doesn't, the battery was likely completely drained, or there's a deeper issue we need to work through.
Check Your Charger and Cable
Since the S26 Ultra doesn't come with a charger in the box, you might be using an older or underpowered one. For a completely dead battery, you need a good USB-C cable connected to a powerful enough wall adapter.
I'd recommend trying a Samsung 25W or 60W Super Fast Charging adapter. Generic chargers or old 5W plugs can take hours to bring a dead battery back to a bootable level. Also, check the USB-C port on the phone itself.
Look for any lint, dust, or debris, especially near the S Pen slot, as it can trap particles that migrate to the port. Gently clean it out with a dry toothpick or compressed air.
Perform a Force Restart
This is different from just holding the power button. A force restart clears the phone's temporary memory and can kick it out of a frozen state. It won't delete any of your personal data.
Press and hold the Volume Down button and the Side/Power button together. Keep holding them for about 10 seconds until you see the Samsung logo appear on the screen, then release.
You should feel a vibration right before the logo shows up. If you see the logo, the phone will continue booting normally. If nothing happens at all, move on to the next step.
Try Wireless Charging
Your S26 Ultra supports Qi2 and Wireless PowerShare. This is a great way to rule out a problem with the physical USB-C port.
Place your phone on a compatible wireless charger. A Samsung 15W wireless charger is ideal. Look for any indicator light on the charger itself to confirm it's receiving power.
If the wireless charger lights up but the phone screen stays black, let it sit for 15-20 minutes. Then try the force restart combo (Volume Down + Power) again while it's still on the pad.
Address a Potential Moisture Detection Error
A known issue with recent Samsung phones is a false "moisture detected" warning that can completely disable charging. Even if your phone is dry, this error can prevent it from powering on.
If you suspect this, power the phone off completely if you can. Then, take a dry cotton swab and gently clean the inside of the USB-C port. After cleaning, leave the phone in a dry, warm place for a few hours without plugging it in.
After waiting, try charging with a different cable and adapter. The system needs to detect that the port is completely dry before it will allow normal charging to resume.
Boot Into Recovery Mode
If the force restart did nothing, you can try accessing the recovery menu. First, connect your phone to a computer or a charger with a USB-C cable.
Press and hold the Volume Up button and the Side/Power button simultaneously. When you see the Samsung logo, release both buttons. You should now be in the Android Recovery screen.
Use the Volume Down button to navigate to the "Wipe cache partition" option. Select it with the Power button, then confirm. This deletes temporary system files and can fix boot issues without touching your data.
Check for Early Software Bugs
The S26 Ultra is a new device running One UI 8.5 on Android 16. Early software bugs, especially after an update, can sometimes cause a failure to boot.
If you can get into Recovery Mode (as described above), see if there's an option to apply an update from ADB or SD card. This is for more advanced users who may have a firmware file ready.
For most people, if a cache wipe doesn't work, the next step in Recovery Mode would be a factory reset. This is a last resort, as it erases everything on your phone.
Consider Battery Protection Settings
It's a long shot if the phone won't turn on at all, but Samsung's Battery Protection feature is off by default. Once you enable it, the Maximum mode limits the charge to 80% to prolong battery health.
If your phone was showing 85% "full" and then died suddenly, it could have had less actual capacity than expected. If you get the phone working again, you can toggle this in Settings > Battery > Battery protection.
Turn off "Battery protection" to allow a full 100% charge, which might prevent unexpected shutdowns in the future.
