The following links are directly to the IPSW files as found on Apple servers. Note the file must save with a “.ipsw” file extension to be usable by iTunes, for best results right-click and choose “Save As”, and consider using a web browser like Google Chrome or Safari to insure the file saves as the proper IPSW format. The files are not .zip, or zipped or archived in any way, and should not be opened with any application other than iTunes.
Prior iOS versions available here:
Most of these versions are no longer signed by Apple and thus impossible to use or downgrade to. Nonetheless, some users may find older versions to be useful for other purposes.