You can delete a list that you don't need anymore, provided you have permissions. If you delete a list by accident, you can restore it from the recycle bin within 90 days or the time your administrator has set.
Note: Some functionality is introduced gradually to organizations that have opted in to the First Release program. If you're not enrolled in the First Release program, or your administrator has set your view to Classic SharePoint, you may not yet see this feature or it may look different than what is described in the help articles.
Delete a list from an SharePoint Online site
From the SharePoint Online site, click Settings , and then click List settings.
Notes: Does your screen look different than the examples here? Your administrator may have classic mode set on the list, or you're using an earlier version of SharePoint. If so, see Add, change, or delete a list or library on a page. If you're a list owner, site owner, or administrator, see Switch the default experience for lists or document libraries from new or classic.
Some features are currently only available in classic mode. Click Return to classic SharePoint in the bottom, left corner of the page to switch to classic mode. To exit classic mode, close all SharePoint windows, and reopen.
In the List settings dialog, under Permissions and Management, click Delete this list.
In the confirmation dialog box, click OK. You'll be taken to the Site Contents window.
Restore a list item using the Recycle bin
Depending on how you or your admin has set up the site, you can restore the list from the Recycle bin for up to 90 days.
Click Recycle bin in the Quick Launch bar.
If you don't see the Recycle bin in the Quick Launch bar, click Settings , click Site contents, and then click Recycle bin in the top right of the screen.
In the Recycle bin dialog, hover over the item you want to restore, and click the check mark.
For more on the Recycle bin, see Empty the recycle bin or restore your files.
If you've cleared your recycle bin, see how to restore from the Second-Stage recycle bin at Manage the Recycle Bin of a SharePoint Online site collection.