Dihyah ibn Khalifa Wahi al-Kalbi was an Arab companion of the Prophet Muhammad. Though prominent in Arabia as the leader of a large clan, his chief claim to fame is as an ambassador from Muhammad to the Roman emperor, Heraclius.
In 630 Dihyah was sent to Roman territory with a message for the emperor. Journeying via Charax and Tarsus, he arrived at Constantinople in October and immediately sought an audience with Heraclius. The latter, having been forewarned by Cyrus of Alexandria and by his own spies in Arabia, was already aware of the new political and religious situation and was eager to discuss it with Dihyah.
Muhammad's message was an invitation for Heraclius to convert to Islam. Though Dihyah was no theologian, he attempted to expain Islam as best he could, emphasising how in many respects it did not conflict with Heraclius' variety of Christianity. After hearing about Muhammad's character, Heraclius was almost convinced but told Dihyah that he could not be certain about trusting the self-claimed prophet without speaking with him himself. He therefore announced his intention to journey incognito to Mecca in order to learn more.
Dihyah began the return journey to Arabia in March 631. On the way, though, he was attacked by robbers led by Al-Hunayd ibn Arid, and was killed as he impetuously tried to fight them. As a result, his news from Constantinople was lost, and when Heraclius arrived the following year it took everyone in Mecca by surprise.