This paper will compare and contrast five distinct models of union with Christ in 16th and 17th century Reformed theology. The “models” to be discussed will be restricted to the various understandings of what the union actually is. The models discussed will be those of John Calvin, William Perkins, John Owen, Thomas Goodwin, and Richard Baxter. All five men, though part of the larger Reformed tradition, had very divergent views on what it meant to be in union with Christ. First will be Calvin’s model. He preferred not to speak about what the union actually is, instead focusing most of his energy on the benefits thereof. He saw a universal scope in the incarnation of Christ but could not give adequate theological weight to it due to his insistence on unconditional personal election of those who would be saved. Second will be Perkins’ model. He made union with Christ the overarching construct of his ordo salutis, but he redefined the union itself to be the infused benefits of the Holy Spirit. Third will be Owen’s model. He held to the concept of totus Christus, the idea that Christ and the believers “coalesce” into one mystical person. Unlike Perkins, Owen believed in a real indwelling of the Spirit in the life of the believer. Fourth will be the more complex model of Goodwin. Goodwin early in his theology held to a real indwelling of the person of Christ and saw his divine nature as the connection point in the indwelling. Later in life, he modified his view to a real indwelling of the Spirit based on filioque that was prioritized over any personal indwelling of Christ. The Spirit became for him the proxy of Christ and that based on eternal procession. Fifth is the view of Baxter, who rejected all talk of real union, preferring instead to reduce the doctrine to a conjunction and contiguity of wills and morals. In the concluding section, the posterity of their views, as they make up the vast majority of the Reformed tradition that follow them, will be discussed as will the general shortcomings of each view.