Tiridates or Teridates or Tirdad or تیرداد is a Persian name, given by Arrian in his Parthica to the brother of Arsaces I, the founder of the Parthian kingdom, whom he is said to have succeeded in about 246 BC. But Arrian’s account seems to be quite unhistorical and modern historians believe that Arsaces continued to rule Parthia until 211 BC.