Insider Movements = Church-planting Movements? In the last few decades, the Church has witnessed a growing harvest of Muslim-background believers coming to Christ. However, a divide remains over whether the “insider” paradigm contributes to the flourishing and multiplication of healthy, biblical churches among Muslims. S. T. Antonio advances this conversation beyond the old arguments through a fresh analysis of the insider paradigm by asking the question, What is church? Starting with the identity-shaping narrative of the people of God, Antonio digs deep into the nature of biblical ekklesia from multiple angles—local and universal, visible and invisible, the classical "marks" of the church, and missional identity. Combining a robust, biblical vision with a nuanced contextualization framework, and informed by firsthand ministry among Muslims, Antonio uncovers the roots and contours of the ecclesial vision of the insider paradigm. Insider Church provides an innovative diagnosis of a paradigm that has been surrounded by controversy, challenging it with constructive analysis for multiplying biblical churches among Muslims. This integrative study draws together biblical, theological, and missiological scholarship in service of Christ’s mission. Insider Church helps guide mission practitioners, leaders, and students toward a wise assessment of insider movements and a vision for church multiplication that is both fruitful and faithful to the Lord of the harvest.