You may need to access the files for your iPhone/iPad/iPod Touch backups on your computer in order to delete or rename them.

Each backup of a device is typically named by the unique device identifier (UDID). You can find your device's UDID by clicking on the Serial Number field in iTunes (which will switch it to your device identifier.) Some folders will have a date/time stamp after the UDID as well.

If you're using an iPhone XS or XS Max, iTunes won't show you your UDID, so you'll need to use one of our other methods to get your UDID on Windows and Mac here.

macOS

On a Mac your backups are in /Users/your username/Library/Application Support/MobileSync/Backup.

• Open Finder, and select the “Go” menu at the top of the screen. Hold the Option key, and select the “Library” menu option from the Go menu. (On OSX Lion and above, Library will only appear with the Option key held.)
• From Library, navigate to Application Support -> MobileSync -> Backup.

Windows

On Windows, your backups are stored in *your user account data folder*\Application Data\Apple Computer\MobileSync\Backup. The user account data location varies for different versions and configurations of Windows.

• Windows 8 and 10: In the Windows search bar type %appdata% (with the percents) and press return/enter. A file browser window will open to the Application Data folder.
• Windows 7, Vista, XP: From the start menu, select Run. In the run box, type %appdata% (with the percents) and press return/enter. A file browser window will open to the Application Data folder.
• From there, navigate to Apple Computer -> MobileSync -> Backup.

Update May 18, 2018: There is now a version of iTunes available in the Microsoft Store as well as from the Apple website. If you installed iTunes from the Microsoft Store for Windows 10, then your backups are stored in a slightly different location.

Windows 10 (iTunes from the Microsoft Store)

• In the Windows search bar paste %userprofile%\Apple\MobileSync\Backup and press return/enter. A file browser window will open to the iTunes backups folder.

I'd be remiss if I didn't say: Make sure you know what you're doing before you muck around in your iTunes backups :)