Heinrich XLV, Hereditary Prince Reuss Younger Line (German: Heinrich XLV Prinz Reuß jüngere Linie; 13 May 1895  – disappeared 1945) was the head of the House of Reuss from 1928 to 1945, as well the last male member of the Reuss-Schleiz branch of the Younger Line.

Heinrich XLV was born at Ebersdorf, in the Principality of Reuss-Gera (present-day Thuringia), only surviving son of Heinrich XXVII, Prince Reuss Younger Line (1858–1928), (son of Heinrich XIV, Prince Reuss Younger Line, and Duchess Agnes of Württemberg) and his wife, Princess Elise of Hohenlohe-Langenburg (1864–1929), (daughter of Hermann, Prince of Hohenlohe-Langenburg and Princess Leopoldine of Baden).

After the war he studied in Leipzig, Marburg, Munich and Kiel, literature, music and philosophy.

In 1923, Heinrich XLV became head of the dramaturgy department at Reussian Theatre in Gera.

The adoption took place for inheritance reasons, not for succession rights for the headship of the House of Reuss.