Fractal geometry tools are used in order to analyze several related problems in surface science, catalysis, and electrocatalysis. The effects of complex morphologies of adsorbents, catalysts, and electrodes on various molecular processes with these materials are determined both theoretically and experimentally. It is shown that fractal geometry provides a convenient and natural tool for the elucidation of geometry-performance relations in heterogeneous chemistry. Issues covered are particle size effects in physisorption and chemisorption; morphology effects on a variety of catalytic processes with unsupported catalysts (including coal liquefaction, alkene polymerizations, oxidations, dehydrogenations, and esterifications); surface accessibility effects on molecular interactions in an Eley-Rideal mechanism; surface patterning effects on concentration profiles near the surface; and electrode-morphology effects on a variety of electrochemical and electrocatalytic processes. The domains of applicability of the fractal approach to these problems is discussed.