Louis the Strict (German: Ludwig der Strenge) (13 April 1229 – 2 February 1294) was Duke of Upper Bavaria and Count Palatine of the Rhine from 1253.

[1] In 1246, the young Louis supported his brother-in-law King Conrad IV of Germany against the usurpation of Heinrich Raspe.

In August 1257 King Ottokar finally invaded Bavaria, but Louis and Henry managed to repulse the attack.

After the young prince's execution in Naples in 1268, Louis inherited some of Conradin's possessions in Swabia and supported the election of the Habsburg Rudolph I against Ottokar II in 1273.

Different sources tell varying tales about how this happened: In 1256, Louis had been away from home for an extended time due to his responsibilities as a sovereign in the area of the Rhine.

Over time a great many tales of folklore sprang up around Louis' deed, most of them written long after his death: Ballad-mongers embellished the tale into a murderous frenzy during which Louis allegedly not only killed his wife after having ridden home for five days and nights, but also stabbed the messenger who brought him the wrong letter; then upon entering his castle, stabbed his own castellan and a court lady and threw his wife's maid from the battlements, before he murdered his wife either by stabbing her or cutting off her head.

Several more restrained chronicles support the account of Marie's execution on 18 January 1256 at Mangoldstein Castle in Donauwörth by ducal decree for alleged adultery, but nothing beyond that.