This book delivers a state-of-the-art overview of the use of electrospun fibers in energy and environmental applications. It first introduces electrospinning and its origins, outlining achievable one-dimensional nanoscaled materials and their applications. It then discusses the use of electrospun materials in energy devices, including low- and high-temperature fuel cells, hydrogen storage, dye-sensitized solar cells, lithium-ion batteries, and supercapacitors. It also explores environmental applications, such as the use of electrospinning-issued materials in membranes for water and air purification, and in sensors and biosensors for pollution control.