Borivoj, as the head of the Premyslids who dominate the environs of present-day Prague, had declared himself kníže—in Latin dux, which means sovereign prince—around the year 870.

His title will be later translated by German scholars as "duke" of the Bohemians (Czechs).

Although the German dukes of the era hold the same title, the meaning of his title is in fact completely different.

In contrast to the German dukes, the Czech dux denotes a sovereign ruler.

Borivoj is recognized as such around 872 by his overlord Svatopluk I of Great Moravia, who dispatches Bishop Methodius to begin the conversion of the Bohemian Slavs to Christianity.

As with most of the early Bohemian rulers, Borivoj is a shadowy figure; exact dates for his reign and vital statistics cannot be established.

Nonetheless, several major fortifications and religious foundations are said to have dated from this time.

In old Czech legends, he is said to have been son of a Bohemian prince named Hostivít.