Track‐etch membranes (TMs) are produced by irradiating polymer films with highly ionizing particles followed by chemical etching. They differ from most conventional polymeric membranes because of their precisely controlled structure. Their pore size, shape, and density can be varied in a controllable manner to produce membranes with the required retention and transport properties. Polymer films are irradiated with either fission fragments or accelerated ions to form the so‐called latent tracks. The process of track etching then converts the latent tracks into hollow channels. Different etching methods have been developed that allow for the formation of cylindrical, conical, funnel‐like, cigar‐like, and other shapes of track‐etched pores. Commercial TMs are produced from polycarbonate, polyethylene terephthalate and polyimide, and their basic properties are presented in this article. TMs are used for diverse applications such as precise filters, model capillary systems, porous substrates, and templates for the synthesis of micro‐ and nanostructured materials.