Ruzaiq (also spelled Ruzayq) was an Iranian nobleman who lived during the 7th and 8th centuries. As the great-grandfather of Tahir ibn Husayn, he was the ancestor of the Tahirids.
Originally a Zoroastrian, he later converted to Islam and became the mawla of Talha ibn Abd Allah al-Khuza'i, an Arab nobleman from the Khuza'i tribe, who served as the governor of Sistan. Ruzaiq's son Mus'ab later played a prominent role in the Abbasid Revolution, and was later rewarded by the Abbasid caliphs by being appointed as the governor of Pushang and Herat. Ruzaiq probably died some years later.