A most important endeavor in modern materials’ research is the current shift toward green environmental and sustainable materials. Natural resources are one of the attractive building blocks for making environmentally friendly materials. In most cases, however, the performance of nature-derived materials is inferior to the performance of carefully designed synthetic materials. This is especially true for conductive polymers, which is the topic here. Inspired by the natural role of proteins in mediating protons, their utilization in the creation of a free-standing transparent polymer with a highly elastic nature and proton conductivity comparable to that of synthetic polymers, is demonstrated. Importantly, the polymerization process relies on natural protein crosslinkers and is spontaneous and energy-efficient. The protein used, bovine serum albumin, is one of the most affordable proteins, resulting in the ability to create large-scale materials at a low cost. Due to the inherent biodegradability and biocompatibility of the elastomer, it is promising for biomedical applications. Here, its immediate utilization as a solid-state interface for sensing of electrophysiological signals, is shown.