In this thesis, I investigate a cluster of sleep phenomena that I classify under the name of “objectless sleep experiences”. By drawing upon descriptions from Indo-Tibetan philosophical traditions, I examine a subgroup of conscious sleep states characterised by the apparent absence of an object of awareness. Some authors describe these experiences as “objectless” or “contentless” inasmuch as they lack awareness of anything; they are states of just consciousness. Here, I consider the construct of objectless sleep awareness to involve a broader range of experiences characterised by the absence of a distinct object of awareness. While they may appear to lack content to the subject, they are not completely devoid of representational content. Despite the growing interest in these states within philosophy of mind, dream and sleep research, there is a significant lack of theoretical work examining this experience. Additionally, most of the descriptions of such a state found in the literature rely highly on anecdotal reports or second-hand sources. This thesis aims to address this gap by presenting the results of two empirical studies that systematically and rigorously collect subjective reports of objectless sleep awareness. Furthermore, I examine current proposals found in the literature characterising a subset of objectless sleep awareness as “lucid”. Lastly, I propose a framework to guide future research on objectless sleep experiences, linking them to associated experiences during both sleep and wakefulness. This framework aims to articulate the similarities and differences among various sleep and waking phenomena, including objectless sleep awareness.