Open the Photos app
Tap Library or Albums
Tap Select
Tap the photos you want to remove
Tap the Trash icon
Tap Delete Photo
To delete from an album, open the album, tap Select, choose photos, then tap the Trash icon
To delete all photos in an album, open the album, tap Select, then tap Select All if available
To remove photos from iPhone but keep them in iCloud, turn off iCloud Photos only if you understand the sync effect before deleting
To permanently delete photos, open Recently Deleted in the Photos app
Tap Select
Tap Delete All or select individual photos
Tap Delete
To delete photos from Messages, open the conversation, tap the contact name, tap Photos, then remove the images if available
To delete photos from Files, open the Files app, select the file, and tap Delete
To delete photos from a computer synced to iPhone, use Finder on Mac or iTunes on Windows and remove the synced album or photos there