There is no option available officially to delete labels from the Gmail app, but you can delete labels by following these steps. 1. Open the Chrome browser on your phone 2. Select the "Desktop site" option 3. Open https://gmail.google.com/ and sign in. 4. Open the web version 5. Select View as the desktop at the bottom of the menu 6. Choose the "latest" or HTML option as per your choice 7. Select labels and delete. For detailed steps with screenshots, check above mentioned steps provided in this post.