Sayn-Wittgenstein-Hachenburg (sometimes called Sayn-Hachenburg) was a German County located in Rhineland-Palatinate, near the river Sieg.

When Count William III of Sayn-Wittgenstein-Sayn died in 1623 without clear heirs, the Archbishop of Cologne occupied the vacant County until the succession was settled.

It was settled by treaty in 1648, when the county was given jointly to Countesses Ernestine and Johanetta, two sisters who were granddaughters of Count William, and their mother Dowager Countess Louise Juliane made regent.

Sayn-Wittgenstein-Hachenburg was inherited by Countess Magdalena Christina in 1661 following Ernestine's death.

[1] The title passed through the female line and is held by the Grand Duke of Luxembourg.