As self-appointed guardians of light who performed many of their activities between sunset and sunrise, medieval monks and nuns had a special relationship with fire, light, and darkness. While medieval monastic authors wrote copiously about light, however, modern scholars have shown comparatively little interest in this topic. Using the concept of lightscape, this essay recreates the unique Latin monastic culture of light of the tenth to thirteenth centuries, considering how religious communities used natural and artificial light as well as darkness to reinforce spiritual lessons, heighten the sensory experience of liturgical life, and signal distinctions between orders in a reform-minded age. Evidence from material culture as well as several textual genres demonstrates that monastic uses of candles, oil lamps, and lanterns reflected the commitment to a strictly regulated life which foregrounded bonds of community and encouraged constant spiritual and physical vigilance. Contemporary understandings of fire and light as heavenly matter also conditioned religious to see everyday light-sources as ready conduits for the miraculous, as well as technologies by which earthly spaces could be made to approximate heavenly ones.