Essential Concepts for a Post-Conciliar Fundamental Moral Theology: Reflections from the Ethics of Jesus in the Beatitudes of Mt 5,3-10 proposes a reflection on the moral issues that plague humanity. There is a philosophical study of the field that some call ethics and others, moral to propose a reflection on moral theology and/or religious ethics. Then there is an attempt to the foundations of contemporary theological ethics. Therefore, the concepts of phenomenology and intentionality are used, in addition to entering the theological anthropology of Edith Stein and the Ethics of the Follow of Jesus of Nazareth. Then, a historical foundation of moral theology is presented, from the post-Tridentine and casuistic horizons to the post-Vatican II context, through its main moralist theologians. Subsequently, an effort is made to reflect on the Beatitudes, with an exegesis and hermeneutics of an ethical-theological nature. Finally, it focuses on the fundamental concepts of Contemporary Moral Theology with a greater emphasis on the concepts of Fundamental Option, Moral Discernment and Conscience.