Open the Contacts app or the Phone app and tap Contacts
Tap and hold a contact, then use Select Multiple if available
Select the contacts you want to delete
Tap Delete
Confirm the deletion
If Select Multiple is not available, use iCloud on a computer
Go to iCloud.com and sign in
Open Contacts
Hold Command on Mac or Control on Windows and click multiple contacts
Press Delete and confirm
If contacts are synced from Gmail or another account, delete them from that account’s contacts list
Turn off contact syncing for an account if you do not want those contacts on your iPhone again