Vratislaus (or Wratislaus) I (Czech: Vratislav I.; c. 888 – 13 February 921), a member of the Přemyslid dynasty, was Duke of Bohemia from 915 until his death in 921.

Around 906, he married Drahomíra, a Hevellian princess, to establish close ties with the Polabian Slavs.

[1] Upon the death of his elder brother Spytihněv in 915, Vratislaus became duke at a time when the Bohemian lands around Prague Castle had already distanced themselves from the political and cultural sphere of Great Moravia and fallen under the influence of East Francia, especially during the rule of Duke Arnulf of Bavaria.

The contemporary Annales Fuldenses report that the Bavarian forces had attacked Prince Mojmír II of Moravia in alliance with the Bohemians already in the year 900.

Vratislaus is credited with the establishment of St. George's Basilica at Prague Castle and also with the foundation of the Silesian city of Wrocław (Breslau), whose Latin name "Vratislavia" denotes his initiative.