When speaking of the future of the human, our attention is often on human beings themselves as a species and their capability to survive in the face of the changes of the world. Our understanding of the human body, space and even our connection with technoscience are vastly transformed by the changes brought by the close and interconnected relationship of human and technology in the contemporary world. From Donna J. Haraway's cyborg to N. Katherine Hayles and Cary Wolfe's discussions on posthumanism, it is undeniable that we have already entered the age of the posthuman. Science fiction as a form of creative writing explores various possible futures of the human species augmented by the advent of technology while posthumanism looks into how the human should respond in view of the changing connection between human and technology, human and animals, human and the earth, and human and nonhuman. Science fiction with a posthuman theme is a unique genre that deals with the human condition in the world of science and technology and its relation to the nonhuman world. This dissertation examines posthumanism, the singularity, and the Anthropocene in science fiction from a thematic perspective. Chapter One reviews the history of cyborg and posthuman theories and the connection between posthumanism and science fiction to illustrate how posthuman discourses and science fiction works develop together. Chapter Two examines the representations of the posthuman body in science fiction along the development of posthuman discourses. Discussions on Mary Shelley's Frankenstein, Bicentennial Man (1999), A.I. Artificial Intelligence (2001), Blade Runner (1982), Blade Runner 2049 (2017), William Gibson's Neuromancer, eXistenZ (1999), and Robert J. Sawyer's WWW Trilogy: Wake, Watch, and Wonder demonstrate four main types of imaginations to illustrate different visions of the posthuman in science fiction: (1) the technologically-made monster, (2) artificial intelligence in an organic body, (3) plugging one's body into the digital realm, and (4) embodiment of the nonhuman. Chapter Three argues for an alternative perspective other than the insistent privileging of the human in posthuman science fiction. From humanistic values and anthropocentric biases to the WWW Trilogy's embrace of the singularity, there is a paradigm shift from humanism to the concern of the nonhuman. The chapter examines Vernor Vinge and Ray Kurzweil's visions of the Singularity with reference to the WWW Trilogy and other singularity science fiction works which portray possible worlds of symbiosis, coexistence, and coevolution. Last but not least, Chapter Four focuses on the Anthropocene and science fiction to illustrate the coevolution of human and nonhuman in relation to the environment and climate change with discussions on Paul Di Filippo's short story "Life in the Anthropocene" and Kim Stanley Robinson's science fictions New York 2140 and 2312. By examining the development of posthuman discourses, concepts of the singularity and the Anthropocene along the creative narratives of posthuman science fiction, this dissertation aims to affirm science fiction's role in exploring the posthuman condition and reimagining our future. It also puts science and humanities together in developing new perspectives and ethics for the world we are in.