Restore deleted sites
Deleted sites are retained for 93 days. After 93 days, sites and all their content and settings are permanently deleted, including lists, libraries, pages, and any subsites.
If you need to retain content for a minimum period of time to comply with industry regulations or internal policies, you can create a retention policy to keep a copy of it in the Preservation Hold library. For info, see Overview of retention policies.
For info about restoring items within a site, see Restore items in the Recycle Bin of a SharePoint site.
For info about restoring deleted sites in SharePoint Server, see Restore deleted site collections using Microsoft Powershell.
Restore a deleted site in the new SharePoint admin center
In the new SharePoint admin center, you can delete and restore all the new types of sites. You can do this even as a SharePoint admin - you don't need to be a global admin.
Sign in to https://admin.microsoft.com as a global or SharePoint admin. (If you see a message that you don't have permission to access the page, you don't have Office 365 administrator permissions in your organization.)
In the left pane, under Admin centers, select SharePoint. (You might need to select Show all to see the list of admin centers.)
If the classic SharePoint admin center appears, select Open it now at the top of the page to open the new SharePoint admin center.
In the left pane of the new SharePoint admin center, under Sites, select Deleted sites.
You can sort and filter deleted sites the same way you sort and filter sites on the Active sites page. You can also sort and filter deleted sites by Time deleted.
Select the site you want to restore.
Select Restore. (If you don't see the Restore button, make sure only one site is selected. The button won't appear if multiple sites are selected.)
Restoring a site that belongs to an Office 365 group restores the Office 365 group and all its resources. Note that the other group resources are retained for only 30 days, whereas the site is retained for 93. If the other group resources have been deleted, you can use the PowerShell command Remove-SPODeletedSite to permanently delete the site.
For info about permanently deleting sites from the Deleted sites page, see Permanently delete a deleted site.