Tiridates III, also known as Tiridates the Great or Tiridates IV, was the Armenian Arsacid king from c. 298 to c. 330. In the early 4th century, Tiridates proclaimed Christianity as the state religion of Armenia, making the Armenian kingdom the first state to officially embrace Christianity.

The Arsacid dynasty, called the Arshakuni in Armenian, ruled the Kingdom of Armenia, with some interruptions, from 12 to 428. The dynasty was a branch of the Arsacid dynasty of Parthia. Arsacid kings reigned intermittently throughout the chaotic years following the fall of the Artaxiad dynasty until 62, when Tiridates I, brother of Parthian King Vologases I, secured Arsacid rule in Armenia as a client king of Rome. However, he did not succeed in establishing his line on the throne, and various princes of different Arsacid lineages ruled until the accession of Vologases II, who succeeded in establishing his own line on the Armenian throne, which ruled the kingdom until its abolishment by the Sasanian Empire in 428.