Reuss, or the Reuss Dynasty, governed counties and principalities in the territory of modern Thuringia in Germany from the 12th to the 20th century. In the 19th century, their holdings included the sovereign principalities of Reuss-Greiz and Reuss-Gera, which remained part of the German Empire until 1918.

The nickname "Reuss," meaning "Russian," belonged to Heinrich I of Reuss, the founder of the younger line of the family in the 14th century. He received it after traveling to Carpathian Rus to fetch his bride Jutta of Schwarzburg-Blankenburg, the granddaughter of Daniel of Galicia, Grand Prince of Kiev and King of Rus.

The Reuss dynasty was distinguished by a unique system of naming and numbering its members. All male members of the family were named Heinrich. Unlike other dynasties that numbered only ruling members, Reuss numbered all males, and the numbers did not necessarily follow in order. For example, the sons of Heinrich LXVII of Reuss-Schleiz were named Heinrich V, Heinrich VIII, Heinrich XI, Heinrich XIV, and Heinrich XVI.

In the senior line of the family, numbering restarted after reaching one hundred members (after Heinrich C, Heinrich I followed), while in the junior line, numbering was updated with the beginning of each new century. The numbers of deceased family members were reused.