Frederick IV (before 30 November 1384 – 7 May 1440), nicknamed the Peaceful (German: Friedrich der Friedfertige) or the Simple (der Einfältige), was a member of the House of Wettin and Margrave of Meissen who ruled as the last independent Landgrave of Thuringia from 1406 until his death.

He was the son of Landgrave Balthasar of Thuringia and his first wife, the Hohenzollern princess Margaret of Nuremberg.

His father had received the Landgraviate of Thuringia in the 1382 Division of Chemnitz and was able to largely extend his territories in several skirmishes with the local nobility.

Landgrave Balthasar planned to marry his son off to Elizabeth of Görlitz, a granddaughter of the late Luxembourg emperor Charles IV; nevertheless, these attempts had already failed, when Frederick succeeded his father in 1406.

One year later he married Countess Anna (d. 1431), the daughter of Count Günther XXX of Schwarzburg-Blankenburg.