Rastislav or Rostislav, also known as St. Rastislav, is the second known ruler of Moravia (846–870).

Although he starts his reign as vassal to Louis the German, king of East Francia, he consolidates his rule to the extent that after 855 he is able to repel a series of Frankish attacks.Upon his initiative, two brothers, Cyril and Methodius, sent by the Byzantine Emperor Michael III in 863, translate the most important Christian liturgical books into Slavonic in his realm.

Rastislav is dethroned by his nephew Svatopluk I, who hands him over to the Franks.