Witness and evangelism are concepts related to how Christians participate in the mission of the triune God (missio Dei). As stated in Together Toward Life, a document published by the World Council of Churches Commission on World Mission and Evangelism (CWME), God’s mission is to share the fullness of life with all creation. God initially shared this life through the act of creation. When humanity rejected life by choosing to sin, God’s mission remained unaltered, with the Father sending the Son and the Spirit to make the fullness of life available to creation again. God’s central act to overcome death and restore life was the incarnation of the Son in Jesus of Nazareth, culminating in Jesus’ crucifixion and resurrection. So all people would be aware of God’s work through Jesus, Jesus commissioned his disciples to share the good news (or gospel) that abundant life is available through God’s grace given through Jesus Christ. Christians become witnesses for Jesus and practitioners of evangelism by communicating the gospel to others and inviting them to receive abundant life by likewise becoming disciples of Jesus (Ekué and Longkumer 2012: 57–58). The term witness can be used as both a noun and a verb. As a noun, it refers to one who testifies about something they have first-hand knowledge of so that others might believe in the message they share. This idea is expressed in the prologue of 1 John: ‘We proclaim to you what we have seen and heard, so that you also may have fellowship with us. And our fellowship is with the Father and with his Son, Jesus Christ’ (1 John 1:3). God can empower anyone or anything to be a witness. This includes individual Christians, groups of Christians, the church collectively, the Holy Bible, nature, or anything else God works through to reveal the gospel and invite others to respond. As a verb, ‘witness’ describes the wide array of activities that Christians can engage in to share the abundant life of God with others. For example, Christians can witness to the gospel through the arts, humanitarian aid, education, healthcare, acts of justice, liturgical practices, or explaining the biblical narrative. Each of these acts can extend a portion of the abundant life of God to others and, by doing so, demonstrate God’s love for creation. Evangelism is the central act of witness. As the CWME states, Witness (Martyria) takes concrete form in evangelism— the communication of the whole gospel to the whole of humanity in the whole world. Its goal is the salvation of the world and the glory of the Triune God. Evangelism is mission activity which makes explicit and unambiguous the centrality of the incarnation, suffering and resurrection of Jesus Christ without setting limits to the saving grace of God. It seeks to share this good news with all who have not yet heard it and invites them to an experience of life in Christ. (Ekué and Longkumer 2012: 67) By presenting the core message of salvation and inviting others to accept it, evangelism stands not only at the heart of witness, but of how Christians participate in the missio Dei. Expanding on a metaphor introduced by David Bosch, missiologist Dana Robert explained, the relationship of evangelism to mission is like the relationship of the heart to the body. Mission is the body […] Evangelism is the heart, both as the pump that circulates the life force and as the seat of the emotions. (Robert 1997: 4) According to Robert, mission encompasses all possible human activities to witness to the gospel. Evangelism provides a foundation in the gospel of Jesus Christ to animate and guide this activity. Even with this clarity about how the terms ‘witness’ and ‘evangelism’ relate to each other and to the larger notion of mission, there is no single definition for each term that is agreed upon by all Christians (Pope-Levinson 2020: 5). For this reason, a framework for understanding what evangelism consists of may be preferable to a single definition. We will address this below with the evangelism equation. In addition to its relationship to Christian mission, evangelism is also an interdisciplinary academic field. The field was formally established in 1973 with the foundation of the Academy for Evangelism in Theological Education as an academic guild. Initially seen as a practical theology that reflected on specific practices of the church (Abraham 1989: 2–3), the field expanded to draw from biblical studies, history, theology, ethics, and a variety of social sciences. Scholars of evangelism seek to understand how God, the evangelist, and those being evangelized relate to one another around the gospel. Evangelism scholars are often followers of Jesus who practise evangelism as well as study it. They therefore take an emic approach to their work as insiders to the Christian tradition, often with the goal of equipping Christian witnesses to elicit positive responses from those they evangelize (Teasdale 2019: 9–12). This article will first look at the origin and authorization for Christians to practise evangelism found in the Bible. Following this is a brief history of witness and evangelism using the missional paradigms described by David Bosch. Using the framework of the evangelism equation the article will then consider how Christians with different experiences, theological perspectives, and contexts have developed different understandings and practices of evangelism. Finally, it will address both criticisms and areas for future exploration related to evangelism.