The son of Hermann I and Sophia of Bavaria, Louis became landgrave of Thuringia when he was only 16.
In 1221 he married the Hungarian princess Elizabeth, daughter of Andrew II. In 1226 Louis was called to the Diet in Cremona, where he promised the emperor Frederick II of Swabia to take up the cross and accompany him to the Holy Land. He embarked for the Sixth Crusade in 1227, partly inspired also by the tales of his father and uncle, who had been to the Holy Land in 1197. Louis left his pregnant wife behind. In the summer of 1227 Louis traversed the mountains between Thuringia and Upper Franconia, through Swabia and Bavaria, crossed the Tyrolian Alps and went along the whole Italian peninsula. After reaching Brindisi, he fell ill of the plague that was decimating the Crusaders’ army in the harbour of Apulia; he received extreme unction by the Patriarch of Jerusalem and went to Otranto where he died just afterwards. A few days after his death, his daughter Gertrude was born. In 1228 Louis’s remains were transferred to Reinhardsbrunn Abbey where he was buried and became object of the people’s devotion. From his wife Elizabeth he had three children: Hermann (1222-1241), who married Helene of Brunswick-Lüneburg; Sophia (1224-1275), who married Henry II of Brabant; Gertrude (1227-1297), abbess of Altenberg monastery.
His wife Elizabeth died a few years after him (1231), at the age of 24 years, and spent the rest of her life as a tertiary of St. Francis, devoting herself to penitence and the service of the poor: she was proclaimed a saint as early as 1235. Although Louis has never been formally canonized, among the German people he became known as Louis the saint (German: Ludwig der Heilige). He is known elsewhere as Blessed Louis of Thuringia.