The Sie + Er Lauf is a pairs race held annually in Vienna's Prater since 1984. It serves as a late-season city, road, and fun run. Each pair covers 2 x 4 km, with one runner completing four kilometres before the other runs the same distance. The race takes place on Prater Hauptallee, near the Stadionbad car park and close to the Ernst Happel Stadium.
The course follows the flat, traffic-free Hauptallee, the main avenue through the Prater. Each runner completes two kilometres out and back to the east, then two kilometres out and back to the west. Teams decide which partner runs first. For most of its history, it was a mixed female-male relay. Now, categories include SIE+SIE and ER+ER pairs, allowing couples, friends, family members, and colleagues to participate. The event typically attracts hundreds of teams, with some years exceeding one thousand teams.