The entry introduces definitions of literacy and their conceptual history to an environmental humanities readership and outlines two key strands in ecoliteracy theory and research: a more traditional and process-oriented one, based on scientific environmental knowledge, and a more recent one focussed on critical cultural and ecological thinking. It links work on ecoliteracy with developments in the environmental humanities, especially in regard to educational research, empirical ecocriticism, and media ecologies. In so doing, it distinguishes ecoliteracy in a stricter and principally science-oriented sense from a broader conception of ecoliteracy as a potential outcome of ecocritical and educational engagement. It concludes by outlining future trajectories in literacy research generally and ecoliteracy studies more specifically.