1. Open WhatsApp and go to the Chats tab.
2. Tap New chat > search for or select the contact you’d like to delete.
3. Tap the contact's name at the top.
4. Tap Edit > scroll to the bottom and tap Delete Contact.

Deleting a contact from your phone's address book won't delete the chat history you have with them. You can find out how to delete a chat in this article.