Have you tried removing the tag from any bookmarks that use it, and seeing if that causes it to disappear from the tags list?

You normally open a Tag folder via the left panel in the Bookmarks Manager (Library) and select all the bookmarks in the right panel and remove them. This will remove this tag from all the bookmarks and remove the no longer used Tag folder like posted above. See also: *https://support.mozilla.org/en-US/kb/categorizing-bookmarks-make-them-easy-to-find ----- If this isn't working then check for issues with the places.sqlite database. If you use Sync then best is to disconnect Sync temporarily during troubleshooting. This could be a problem with the <b>places.sqlite</b> and <b>favicons.sqlite</b> files in the Firefox profile folder. *use the "Places Database" -> "Verify Integrity" button on the "Help -> More Troubleshooting Information" (about:support) page If errors are reported with "Verify Integrity", close and restart Firefox or reboot and retry. See also: *https://support.mozilla.org/en-US/kb/fix-bookmarks-and-history-will-not-be-functional *https://support.mozilla.org/en-US/kb/cant-add-change-or-save-bookmarks You can use the button on the "Help -> More Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the <b>about:profiles</b> page (Root directory). *Help -> More Troubleshooting Information -> Profile Folder/Directory:<br>Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder *https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

I have no bookmarks, so I'm going to try the second method by cor-el now.