Baldwin V (1177-1186) was the son of Sibylla of Jerusalem and her first husband, William of Montferrat. He was the nominal king of Jerusalem from 1183 to 1186, under the regency of Raymond III of Tripoli. During his reign, Saladin continued to advance into the kingdom, which had been weakened during the reign of the leprousBaldwin IV. Sibylla and her second husband Guy of Lusignan allied with Raynald of Chatillon against Raymond III during Baldwin V's reign, when Baldwin died as a child in 1186 Sibylla became queen with Guy as her consort. Guy, however, had all the real power, and soon faced the final invasion by Saladin that would result in the capture of Jerusalem.
Baldwin was the son of BaldwinV of Hainaut, and Margaret I, sister of Philip of Alsace and Countess of Flanders.
Baldwin took possession of a much-reduced Flanders, for his uncle had given a large chunk, including Artois, as dowry to Baldwin's sister Isabelle of Hainaut on her marriage to King Philip II of France, and another significant piece to his own wife.
Baldwin's uncle William of Thy (an illegitimate son of Baldwin IV of Hainaut) was regent for Hainaut.
He was crowned co-King of Jerusalem with his uncle, Baldwin IV in 1183, and once his uncle died, became the nominal king from 1185 to 1186, under the regency of Raymond III of Tripoli.
BaldwinV died soon after his accession, and after his funeral Sibylla was proclaimed Queen by the Patriarch, which the Haute Cour later endorsed.