Here’s how you can hide Hangouts in the Gmail:
- Sign in to your Gmail account.
- Hit the Gear icon at the top right.
- In the menu, hit Settings option which you can find between Configure inbox and Themes.
- Navigate to Chat tab which you can find between Add-ons and Advanced.
- Select Chat off.
- Hit the Save Changes button.
Note: If you want to show Hangouts, then follow the above steps, and instead of selecting Chat off, choose Chat on.