The aim of this dissertation is to explore the current turn to liveness within the media arts through an analysis of the live televisual transmission. In specific, I posit that this turn is actually a return, and frame contemporary live televisual works as a part of a rich, but understudied, media art genre marked by a long history of experimentation with the live transmission as an artistic medium. I argue that artists across media generations have worked to distinguish the live televisual transmission as an art form through a strategic leveraging of the medium's most basic characteristics: co-presence, unpredictability and leakiness. To demonstrate this, I analyze a range of live televisual transmission artworks beginning with Lucio Fontana's Luminous Images in Movement (1952) to recent live streaming projects that utilize social media broadcasting platforms. I critically read across the live televisual transmission across four genealogies of practice to determine how artists: 1) developed an aesthetics of the live transmission distinguishable from both visual arts practices and mainstream media; 2) activated the live transmission as a two-way send and receive link to establish a spatial and temporal co-presence in which artist and viewer shared screen space in real-time; 3) introduced unpredictability to the live transmission as a strategy to interpellate viewers and enhance participation; and 4) exploited the inherent leakiness of the live televisual transmission to create unique spectatorial experiences that revealed its materiality and countered hegemonic control of the airwaves. I conclude with a brief exposition on the future of the live televisual transmission as an artistic genre by examining emerging practices of live witnessing.