Union with Christ is a crucial theme for Reformed soteriology with far-reaching implications in numerous areas, including the theology of the covenant, the sacraments, eschatology, and the outworking of the doctrine of grace as justification and sanctification in Christ. Through engagement with scriptural exegesis and the refining of various catholic and characteristically Reformed elements, a Reformed doctrine of union with Christ has much to offer to the broader theological and ecclesial discussion. Rather than reducing salvation to simply a forensic act or a gradual transformation, the Reformed tradition holds together God’s forensic declaration with the Spirit’s indwelling, transformative work. Rather than approaching the various acts of God in salvation as temporal stages for human ascent to God, God’s electing action unfolding in justification, adoption, sanctification, glorification are ‘manifestations’ of union with Christ. Rather than reducing salvation to a purely vertical or purely horizontal affair, the Reformed hold together communion with God in Christ with covenantal, reconciled communion with others who are adopted into his household. This cluster of topics continues to generate considerable debate and development in contemporary biblical and theological circles, and promises to be an area for lively discussion for years to come.