Hærvejen (Danish, literally: the army road, German: Ochsenweg, literally: oxroad) is the name given to an ancient trackway in Denmark and Schleswig-Holstein. The route passes from Viborg over Flensburg to Hamburg, the territory of which it entered at Ochsenzoll ("ox-toll", "toll" in the meaning of "customs") and where it connected with other roads. It has been known by several other names throughout history, most importantly "the Cattle Road" (Studevejen) and "the Ox Road" (Oksevejen / Ochsenweg).
The road runs more or less along the watershed of the Jutland Peninsula, similar to the ridgeways in England. By using this route one could avoid rivers, or ford them close to their origins where they were still shallow. As time went by this route was improved with paved fords, embankments and bridges. Concentrations of mounds, defensive ditches, settlements and other historic landmarks can be found along the road. While sections of it can be traced as far back as 4000 BC, newer road construction has erased many traces. The use of the road declined during the Viking age, as transportation by ship became more convenient. New cities were constructed along the coast instead of the road.
In the southern, narrow part of the peninsula the trackway followed the edge of western marshes and eastern moraine country. Near Haderslev, Åbenrå, Flensburg, and Schleswig, it branched into western bypasses on the hills and accesses to the towns, each of them localized at the inner end of a long, narrow bay. One of the southern ends of the the Ochsenweg has given its name to a suburb of Hamburg: Ochsenzoll is the locality of the ancient custom post.
Today modern highways follow the route of the old road. At a few places it is still possible to see the old tracks, embankments, sheep pens and fords. Parts of it have been converted into a long-distance walking route. A popular walk known as Hærvejsmarchen takes place each year. An international cycle route has been marked from the Elbe to Viborg.