What is the church? Why are there so many different expressions of church throughout time and space, and what ties them all together? Ecclesiology-the doctrine of the church-has risen to the center of theological interest in recent decades. In this text, theologian Veli-Matti Kärkkäinen provides a wide-ranging survey of the rich field of ecclesiology in the midst of rapid developments and new horizons. Drawing on Kärkkäinen's international experience and comprehensive research on the church, this revised and expanded edition is thoroughly updated to incorporate recent literature and trends. This unique primer not only orients readers to biblical, historical, and contemporary ecclesiologies but also highlights contextual and global perspectives and includes an entirely new section on interfaith comparative theology. An Introduction to Ecclesiology surveys - major theological traditions, including Eastern Orthodox, Roman Catholic, Reformed, and Pentecostal - ecclesiological insights from Latin American, Africa, and Asia - distinct perspectives from women, African Americans, and recent trends in the United States - key elements of the church such as mission, governance, worship, and sacraments - interreligious comparison with Jewish, Islamic, Hindu, and Buddhist communities As the church today encounters challenges and opportunities related to rapid growth in the Majority World, new congregational forms, ecumenical movements, interfaith relations, and more, Christians need a robust ecclesiology that makes room for both unity and diversity. In An Introduction to Ecclesiology students, pastors, and laypeople will find an essential resource for understanding how the church can live out its calling as Christ's community on earth.