Marcus Junkelmann (born 2 October 1949 in Munich) is a German historian and experimental archeologist.

Junkelmann was born in Munich to the art historian Erich Junkelmann and his wife Charlotte. The family soon moved to Schleißheim and took residence in the Lustheim_Palace, where Junkelmann spent his youth. He graduated 1969 from the Dom-Gymnasium Freising (high school) and started to study history at LMU Munich in 1971. In 1979, he received his PhD for a thesis on the military achievements of Maximilian II (1662–1726) (original title: Kurfürst Max Emanuel von Bayern als Feldherr). After that he worked as an associate member of staff at the university and for the Bayerisches Armeemuseum (military museum) in Ingolstadt.

In the 1980s Junkelmann became well known in Germany for his work in experimental archeology. He reconstructed and tested Roman weapons and army gear. In 1985 in connection with the 2000-year celebration of the city of Augsburg he organized a large experimental reenactment of the life and work conditions of Roman legionaries. The experiment consisted of a month-long march from Verona to Augsburg including a crossing of the Alps. For the complete trip the original Roman army gear and equipment was used and the typical legionary tasks were performed. Later Junkelmann went on to perform similar experiments for the Roman cavalry. He authored several books and documentaries on his archeological experiments. In 1997, he was awarded the Ceram Prize for his book on the nutrition of Roman soldiers (original title: Panis militaris: Die Ernährung des römischen Soldaten oder der Grundstoff der Macht).

In 2012 Junkelmann was awarded the Bavarian Order of Merit.