Negrelli Viaduct (also called Karlín Viaduct, formerly generally the State Railway Company Viaduct) is a railway bridge over the Vltava River and a viaduct in Karlín, which connects Masaryk Station in Prague across the island of Štvanice with Bubny, named after its builder Alois Negrelli. It is historically the first Prague railway bridge and the second oldest preserved Prague bridge over the Vltava River, the thirteenth in order along the Vltava River. With a length of 1,120 m, it is the longest railway bridge and the fourth longest bridge overall in the Czech Republic. Until 1910, it was the longest bridge in Europe and is still the longest railway bridge in Central Europe.
The beginning of the viaduct lies in the part of Nové Město falling into Prague 8. Above the Florenc bus station, it forms the border between Nové Město and Karlín, then continues through the territory of Karlín across the Vltava island of Štvanice to the Bubny part of Holešovice.