Check if your contacts are hidden in the Contacts app
Open the Contacts app and pull down to refresh
Make sure the correct account is enabled in Settings > Contacts > Accounts
Turn Contacts sync off and back on for iCloud, Gmail, or other accounts
Sign in to iCloud.com and check whether your contacts are still there
Restore contacts from iCloud.com if they were deleted recently
Check Settings > [your name] > iCloud > Contacts and enable it
Make sure Contacts is enabled under Settings > Apps > Contacts > Accounts
Restart your iPhone
Update your iPhone to the latest iOS version
Check if you recently changed your default contacts account
Restore contacts from an iCloud backup if needed
Restore contacts from a computer backup if you have one
Check your email accounts for synced contacts
Verify that your contacts are not filtered out in the Contacts app
If using Google contacts, confirm sync is on in your Google account settings
If contacts are still missing, contact Apple Support