Porphyrins and related tetrapyrroles have been extensively studied because of their importance in biological processes and they are often used in the development of artificial photosynthesis, catalysis, and sensor systems. Challenges in the development of functional nanoscale porphyrin systems are many, including the need to organize the porphyrins (e.g., to facilitate processes such as energy- and electron transfer) and to couple the porphyrin nanostructures to other nanoscale components (e.g., catalytic elements and conductors) to produce multifunctional nanoscale systems. This article summarizes recent advances in the synthesis of discrete self-assembled porphyrin nanostructures with well-defined shapes and sizes. A novel method for growing metal on the porphyrin nanostructures to produce nanocomposites with metal catalysts or interconnects is also described. Current and potential applications of these nanostructures and porphyrin-metal nanocomposites are discussed.