Sayn-Wittgenstein-Sayn-Altenkirchen was a German county.

When Count Wilhelm III of Sayn-Wittgenstein-Sayn died with no clear heir, the Archbishop of Cologne occupied the County until it was settled with a treaty in 1648, when the County was given jointly to Princesses Ernestine and Johanette, two sisters who were granddaughters of Count Wilhelm, and their mother Dowager Countess Luise Juliane was made regent, but shortly after the County was split between the two. Ernestine's portion was called Sayn-Wittgenstein-Hachenburg (or Sayn-Hachenburg for short), a title which descended through the female line and is now a title of the Grand Duke of Luxembourg, while Johanette's was Sayn-Wittgenstein-Sayn-Altenkirchen (or Sayn-Altenkirchen for short). Their mother remained regent for both Counties until 1652, when Johanette and Ernestine separately ruled their respective Counties. Sayn-Altenkirchen was inherited by Wilhelm Heinrich, Johanette's son, then when he died childless, it was inherited by Karl, Johanette's great-grandson and Wilhelm Heinrich's great-nephew.

The County of Sayn-Wittgenstein-Sayn-Altenkirchen ended when it was given to Nassau in 1803.

Queen Caroline of the United Kingdom, wife of George II, was co-heiress to this County, but she never inherited it, and her grandson George III was compensated for his loss of inheritance to it.

Counts and Countesses of Sayn-Altenkirchen