Marcel Koehler (1854-1931) was a French structural engineer, known primarily for his crucial role in the design of the Eiffel Tower. He worked for the Compagnie des Établissements Eiffel, where, along with his colleague Maurice Koechlin, he conceived the first sketch of the tower in 1884. Their initial design, based on a large lattice pylon, became the basis for the final structure realized by Gustave Eiffel. His career also includes significant contributions to other iconic works, such as the internal structure of the Statue of Liberty and the Garabit Viaduct, projects in which he applied his expertise in metal structures. For his merits, Koehler was named a Knight of the Legion of Honour. His name is also engraved on the facade of the first floor of the Eiffel Tower, along with those of 71 other scientists and engineers who contributed to its construction.