Louis I, Count of Sayn-Wittgenstein, nicknamed "the Elder", formally "Louis I of Sayn, Count at Wittgenstein" ruled the County of Wittgenstein, on the upper reaches of the rivers Lahn and Eder, from 1558 until his death. He converted his county to Calvinism and was an influential politician in the service to the Electoral Palatinate.

Sayn-Wittgenstein was a county of medieval Germany, located in the Sauerland of eastern North Rhine-Westphalia.