Christian mysticism is the tradition of mystical practices and mystical theology within Christianity which "concerns the preparation [of the person] for, the consciousness of, and the effect of [...] a direct and transformative presence of God" or Divine love. Until the sixth century the practice of what is now called mysticism was referred to by the term contemplatio, c.q. theoria, from contemplatio, "looking at", "gazing at", "being aware of" God or the Divine. Christianity took up the use of both the Greek (theoria) and Latin terminology to describe various forms of prayer and the process of coming to know God.

Mysticism is popularly known as becoming one with God or the Absolute, but may refer to any kind of ecstasy or altered state of consciousness which is given a religious or spiritual meaning. It may also refer to the attainment of insight in ultimate or hidden truths, and to human transformation supported by various practices and experiences.