Sign in to your Google Account
Go to the Google Account settings page
Click Data & privacy
Scroll to Data from apps and services you use
Click Delete a Google service
Sign in again if prompted
Find Gmail and click the trash icon
Enter an email address for another Google service if required
Check the confirmation email sent to that address
Open the email and follow the link to confirm deletion
Review the consequences and confirm deletion
If you want to delete the entire Google Account, go to Data & privacy
Click More options
Click Delete your Google Account
Follow the prompts to confirm account deletion