The selective nitration of meso-tetraphenylporphyrin complexes is described. The reaction of the above porphyrinates with 25% HNO₃ or 5% HNO₃ at room temperature or 0-5 °C, respectively, results in the formation of the corresponding mono β-nitroporphyrins (56-81%), accompanied by small amounts of a mixture of β,β-dinitro by-products. The results described above are the first known examples of β-mononitration of meso-tetraarylporphyrin complexes under electrophilic conditions. Reactions with nickel(II), copper(II), and cobalt(II) porphyrinates are discussed.