<p>Ceramic nanofiber architectures are useful for a wide range of applications, including lightweight structures, filtration, and catalyst supports, due to their high specific surface area, chemical resistance, and thermal stability. To date, ceramic nanofibers have been predominantly fabricated by electrospinning; however, controlling nanofiber alignment within complex architectures is not possible by this technique. Here, we report the in-situ generation of aligned ceramic nanofibers that form through a combination of polymer self-assembly and additive manufacturing. Specifically, preceramic polymer and block copolymer feedstock blends were observed to phase separate during the heat treatment of printed filaments. Nanofiber alignment appears to be influenced by confinement effects imposed on the self-assembling polymers by the printed filament geometry. Following curing, the printed structures were pyrolyzed to generate complex objects composed of ceramic nanofibers. As exemplars, we have printed one-dimensional nanofibrous tows, springs, and lattices that can be manipulated by bending and twisting without mechanical failure.</p>