The new materialist term "entanglement" refers to the inextricable, mutual, and nondual relationship between humans, nonhumans, and environments within a planetary collective. Overall, new materialist theory has a strong focus on embodiment and material entanglement. Correspondingly, New Wave Science Fiction (SF) novels from the 1960s and 1970s represent different kinds of relations between humans, nonhumans, and environments, but with a striking focus on what J. G. Ballard calls "inner space". As works of literature with human protagonists, the New Wave SF novels selected for analysis in this thesis—J. G. Ballard's The Drowned World (1962) and The Drought (1964), Frank Herbert's Dune (1965), and Ursula K. Le Guin's The Word for World is Forest (1972)—represent not only human/nonhuman material entanglement but also what this thesis refers to as human "psychological entanglement" with the nonhuman world. While this psychological entanglement is notably absent from new materialist theories of entanglement, it is nevertheless represented in the New Wave SF examined. These fictions depict the psyche as entangled with ecological systems. Additionally, this material entanglement with the nonhuman renders the human psyche more-than-human too. To this end, New Wave SF writers depict "psychological entanglement" as an experience of deep psychic contact with "inner space." The term "contact with inner space", in the context of this thesis, refers to the fusion of human internal mental states with external environments, including complex ecosystems. This "contact" or entanglement, therefore, possesses both a physical and psychological dimension, and in the four New Wave SF novels analysed in this thesis, it takes multiple forms" including, human contact with inner space, intra-action with environments, symbiosis with ecology and geological time, nonduality with ecosystems, and immanence within forest ecosystems. Ballard, Le Guin, and Herbert's literary representation of these entanglements reveal how characters psychologically relate to, or experience, particular environmental problems such as climate change, drought, aridity, and deforestation. Therefore, this thesis asks two questions: First, how does the intersection of characters' contact with inner space in The Drowned World, The Drought, Dune, and The Word for World is Forest and new materialist theory of entangled human/nonhuman relations suggest an extension of "entanglement" to include "psychological entanglement"? Second, how do Ballard, Herbert, and Le Guin's representations of "psychological entanglement" in these New Wave SF novels challenge the rationalist and anthropocentric assumption of a human/nonhuman dualism? By contesting this dualism, these SF writers undermine human exceptionalist thinking long linked to the perpetration of global environmental harms, including climate and deforestation crises.