The Army Group Mackensen (German: Heeresgruppe Mackensen) which operated in Serbia between 18 September 1915 and 11 October 1916 during World War I under the command of field marshal Mackensen, was an Army Group of the German Army.
This Army Group was established in September 1915 to invade Serbia.
The invasion began on 7 October 1915 and by the end of January 1916, the whole of Serbia, Montenegro and the largest part of Albania were in the hands of the Central powers.
After that, the front stabilized on the Greek - Macedonian Border.
On 30 July 1916, Field Marshal Mackensen left for the Romanian Front and the Army Group was temporarily commanded by the Bulgarian High Command.