Deleting an iCloud backup
Settings → your name → iCloud → Manage Account Storage → Backups. Every device that has ever backed up to this account is listed with its size and last backup date. Tap one and choose Delete Backup.
Backups for phones and iPads you no longer have are pure waste and safe to remove. On accounts that have been through several devices, this alone often frees several gigabytes.
The one that catches people out
Deleting the backup for the device you are currently holding also turns off iCloud Backup for it. iOS warns you, but the wording is easy to skim past, and the result is a phone with no backup and no schedule to make one.
If you delete the current device's backup to free space, go straight back to Settings → your name → iCloud → iCloud Backup, switch it on again and tap Back Up Now.
Shrinking a backup instead of deleting it
Under Manage Account Storage → Backups → this iPhone, each app is listed with the size of its backup data and a switch. Turning off apps storing gigabytes you do not care about shrinks the next backup considerably without removing the backup itself.
Be deliberate: an app switched off here is not in the backup, so a restore will bring it back empty. Games and apps holding large downloaded caches are the sensible candidates.
Deleting computer backups on a Mac
Connect the iPhone, select it in Finder, click Manage Backups. Every backup on that Mac is listed with its date; right-click to delete or to archive. Each full backup is tens of gigabytes, so old ones are worth clearing.
Take care not to delete an archived backup you made deliberately before an update — that is exactly the one you might need.
Deleting computer backups on Windows
The Apple Devices app has an equivalent backup list under the device's settings. On older iTunes installs it lives under Preferences → Devices, where backups can be selected and deleted.
As on a Mac, check the dates before deleting. A backup made just before a major update is the one worth keeping.
Keep at least one good backup
The point of clearing old backups is space, not tidiness. Before deleting anything, confirm you still have a current backup of every device you actually use — the date on Settings → your name → iCloud → iCloud Backup for the phone in your hand.
Our guide to checking backup dates covers where to look for each type.
Frequently Asked Questions
How do I delete an old iCloud backup?
Settings → your name → iCloud → Manage Account Storage → Backups, select the device and choose Delete Backup.
Is it safe to delete a backup for a device I no longer own?
Yes. Those are pure waste and removing them is the easiest way to reclaim iCloud storage.
What happens if I delete my current iPhone's backup?
It also turns off iCloud Backup for that device. Turn it back on afterwards and run a new backup.
How do I delete backups on a Mac?
Connect the iPhone, select it in Finder and click Manage Backups, then right-click a backup to delete it.