The Russian Sixth Army was a World War I Russian field army that fought on the Eastern theatre of war.

The 6th Army Field Headquarters was established in July 1914 at the Saint Petersburg Military District. Between July 1914 and December 1916, the Army was tasked with defending St. Petersburg and the Baltic and White Seas' coasts. In August 1915, it became part of the newly formed Northern Front. With the creation of the Romanian Front in December 1916, the staff was transferred to the Danube Army in Romania, which was renamed the 6th Army. The old 6th Army units became part of the Northern Front.