The rational design of ultralong carbon nitride nanostructures is highly attractive due to their high aspect ratio alongside their high surface-to-bulk ratio, which make them suitable candidates for various applications such as photocatalysts, water treatment, and sensors. However, the synthesis of ultralong, continuous carbon nitride wires is highly challenging. Here we report the synthesis of 4 cm long and large lateral size carbon nitride wires by utilizing unique supramolecular spheres composed of graphitic carbon nitride (g-CN) monomers as the reactants. In situ scanning electron microscopy studies reveal that upon calcination the g-CN wires spontaneously start to grow from the spheres, while the remaining assembly which acts as a substrate creates self-standing carbon-rich g-CN porous films. The different morphology, chemical composition, and electronic properties of the wires and carbon-rich g-CN allow their utilization as both photocatalyst and water cleaning materials. The g-CN wires exhibit excellent photoactivity for hydrogen production whereas the porous carbon-rich g-CN porous film can be efficiently used for water cleaning applications. The reported work opens opportunities for tailored design of g-CN nanostructures and their use as multifunctional materials for photocatalysis, sensing, and other energy-related applications.