Q:

How to Disable welcome message in header file in magento 2?

How to disable Welcome message in magento 2.3

A:

Go to

magento2/vendor/magento/module-theme/view/frontend/templates/html/header.phtml

and remove the <li> tag marked in the picture below.

If using any custom theme, you may find the relevant file in app/design/theme directory and modify code in that file.
Run upgrade and cache commands, and you're good to go.
Also you can remove the message from admin panel as shown from below location:

But, this will still display the username if customer is loggedin.

