Why am I seeing a stranger’s email linked to my Google account?

This same exact thing happened to me this morning. I was checking my personal email and clicked on my profile to switch accounts to check my work email and I couldn't. I had [email protected] on the screen where I would normally select a different account to switch to and my only option was to click "Done" or swipe the screen back down and exit the gmail app. I was afraid to click "Done". I have never received any emails from [email protected] so I was unable to 'block' but I created a filter to automatically delete any emails I get from this address. So glad there were some solutions here. I changed my password, updated my backup email, added my phone number and turned on 2-Party Verification. I had gmail signout of all devices. Then I removed the gmail app from my phone and reinstalled it from the apple app store. I also installed a VPN (free from my workplace). I then updated my iOS. Good grief that was annoying, Lol. I had way better things to do with my day, but I suppose it's good that my phone is more secure now. Thanks everyone for the solutions!

Oh, this was for my iPhone, not a desktop.

I just had the same issue. I could find no mention of that e-mail address in either the address book, security preferences or various incoming e-mails.
So I thebn deleted the g-Mail app, re-installed it, disconnected all accounts, and then re-attached them. The pop-up screen then disappeared.

It could just be that someone else got their account hacked and it’s showing up in yours by mistake. Keep an eye on anything weird, but it might not be about you!

First things first, check if any of your files are shared. Make sure everything is set to private and look for any unfamiliar associated emails in your Google account. A friend of mine had a similar situation where someone hacked his account and set up email forwarding, making it hard for him to regain access. To prevent this from happening, consider using a two-factor authentication app or a security token like Google Titan or Yubikey. This way, you’ll need that token to log in and it adds a layer of protection!

Yeah, this sounds kind of sketchy. You might want to block the email just in case. Also, did you accidentally click on anything suspicious or download something? That's often how these hackers get in.