How to remove your WhatsApp account
In WhatsApp, go to the main menu, Settings, Account, and choose the last option (Delete my account). This will remove everything. You will probably want to delete the app from your phone too.
Helpful Trick: Removing online data
Publicly visible text/images often aren’t properly removed even when you succeed in removing an account. Try editing or removing them manually before removing the account itself. If you’re unsure what happens to your tracks: this can be found mostly in the Terms of Service/Privacy Policy; otherwise you can always contact WhatsApp and ask personally. By the way, removal requests don’t necessarily mean your data will actually be removed (e.g. due to legal obligations).
Helpful Trick: Remove third-party logins
If you signed up for WhatsApp using a third-party login such as Facebook or Twitter, you probably want to revoke all access from WhatsApp. Click here to find out how.