Ju Mipham Namgyal is one of the best known authors of the Nyingma tradition. He was a prolific writer with an extraordinary knowledge of his own and others' dharma traditions. He wrote several texts on the topics of the most profound level of Great Completion (Dzogpa Chenpo). The text here is one of his texts on Thorough Cut (Tregcho). The wording of the title "Preserving the Face of Rigpa" is explained in the introduction by the author. Briefly, it is saying that this text focusses on one specific aspect of Thorough Cut practice called "preserving rigpa". The remainder of the title, "The Essence of Wisdom", refers to the fact that this technique of preserving rigpa really is the essential technique for developing wisdom. The text is short but has become one of the core texts used in Tibet to teach this specific aspect of Thorough Cut practice. Because it is so popular within the Tibetan tradition and because it is one of the few texts that deals specifically with this subject, we felt that it was a worthy addition to our selection of texts on the subject of Thorough Cut. Therefore, we have translated it and made a book out of it. Note that, although this text was written as part of Dzogchen instruction, it is equally applicable to the practice of essence Mahamudra. Thus the text is ideal for anyone who is practising either of the two. A short but clear introduction makes the content of the text accessible.