On November 11, 2017, the world's first railway bridge built in reinforced UHPFRC on a main railway line lane was put in service. The building project of the Swiss Federal Railways was realized within a replacement project of a double‐lane railway bridge of short span at Sempach in the Canton of Lucerne, Switzerland. UHPFRC is a novel cementitious fibre‐reinforced composite material of high strength and durability that provides ideal properties for application to structures of transportation infrastructure. In addition to lower life cycle costs, the modular construction method including a high prefabrication degree allows for shorter construction time and thus reduced service restrictions. The UHPFRC structure with a span of 6.0 m was equipped with a monitoring system to capture the structural behavior due to train crossings. First results of the measurements confirm the expected values that lie significantly below the calculated values. This article describes the design, dimensioning, execution and monitoring of this novel bridge structure.