This study probes the eucharistic implications of the doctrine of the Trinity in the theology of John Calvin (1509-1564). Calvin scholarship has established that the doctrine of the Trinity is the key paradigm of divine-human relationship in Calvin’s theology. Drawing upon this, this study explores how the doctrine affects Calvin’s concept of divine-human interplay in worship and the Lord’s Supper, and how it has liturgical implications for both disciplines. After a reflection on the connection between the doctrine of the Trinity and worship and the sacraments in Calvin’s thought, this thesis shows that the doctrine of the Trinity is an underpinning paradigm for Calvin’s distinctive understanding of the Lord’s Supper as a heavenly communion, a concept by which a personal, experiential, and dynamic, nature of eucharistic communion is highlighted. It also provides surveys of the meaning of the eucharistic heaven, and of the actual mode of the heavenly communion in the ministry of the church, along with a consideration of how this Trinitarian doctrine of the Lord’s Supper distinguishes Calvin’s liturgical thought and practice from those of other reformers. From these surveys it is concluded that the doctrine of the Trinity is the essence of Calvin’s theology and practice of the eucharist.