Arda (Armenian: Արդա) was the 2nd wife of King Baldwin I of Jerusalem. She was the first Queen consort of the Kingdom of Jerusalem, as Baldwin's brother and predecessor Godfrey of Bouillon was unmarried.
Her name is unrecorded in contemporary sources, but since the 17th century she has been traditionally called Arda. She was the daughter of a minor Armenian noble named Thathoul (or Thoros), lord of Marash. Baldwin married her in 1097 after the death of his first wife, Godehilde, who had travelled with him on the First Crusade. Thoros promised 60,000 bezants as a dowry. This was a politically convenient marriage, as Baldwin was the first Count of Edessa, a crusader state carved out of Armenian territory in Mesopotamia.
Baldwin succeeded his brother as King of Jerusalem in 1100, but Arda did not immediately accompany him south; she travelled by sea and arrived probably in 1101. In 1105 Baldwin had the marriage annulled, supposedly because Arda had been unfaithful, or, according to Guibert of Nogent, because she had been raped by pirates on the way to Jerusalem. In reality, Thoros had paid very little of the dowry, Arda had produced no children, and an Armenian wife was less useful in Jerusalem than in Edessa. Fulcher of Chartres, the chronicler closest to Baldwin, does not mention the matter at all, which likely means that Baldwin had no legitimate reason to annul the marriage. Instead, he simply forced Arda to enter the monastery of Saint Anne. Arda later demanded to be released and went to Constantinople, where her father had fled when his lands were taken over by Edessa.