The Siège of Saint-Jean-in Acre in 1191 is an military operation of the Third crusade (1189 - 1191).

In July 1188, Saladin gives in freedom Guy de Lusignan, king of Jerusalem captured the previous year with the Bataille of Hattin, after him to have made solemnly swear not to take the weapons against the Moslems more.

In August 1189, Guy de Lusignan, disavowing his word, puts the seat in front of the port of Acre. It has modest forces, but each day of the ships charged combatants arrive from Occident in reinforcement (September). The city is doubly encircled: around the ramparts, the Francs form an arc of circle, but must count, on their backs, with the army of Saladin, which tries to take them out of clipper.

In October, Saladin learns the arrival close to Constantinople from the emperor to Germany Frederic Barberousse, with 200 to 260.000 men. Saladin calls all the Moslems with the Jihad.

The seat of Acre enlise. Saladin, anxious of advanced of Barberousse in minor Asia, could not carry out of final offensive. The belligerents agree truces during which they banquètent and devote themselves to plays. But the epidemics make devastations, and during winter 1189/1190, the supply of besieged is not easy, especially that the maritime blockade is done more rigorous. By twice however, Egyptian fleets manage to arrive to the port, at the price of heavy losses. Saladin must have recourse to the trick. In July, it makes arm with Beirut a ship charged with supply. Its crew is equipped like Francs, crosses are fixed on the masts, of the pigs highlighted on the bridge. He manages to break the blockade.

Barberousse, victorious on the Turks with Iconium in May 1190, drowns in Cilicie while crossing the Selef (June 10th). Tested by the difficulties of the way, then by an epidemic which is declared with Antioche, its army disperses. A few hundreds of knights only will take part with Frederic de Souabe in the seat of Acre.

In April 1191, the king of France Philippe Auguste unloads in the vicinity of Acre with his troops. The king of England Richard Lion-hearted at the beginning of June joined it, with 25 galères, after being himself seized Cyprus. Richard who wishes to meet Saladin, comes into contact with his brother Al-Adel, but without results. July 11th, the inhabitants of Acre, in prey with the famine, capitulate after two years of seat. Richard makes massacre the garrison of the city, 2700 soldiers, with nearly 300 women and children of their family.

Philippe Auguste leaves the Palestine in August. Richard walks towards the south, along the coast, while Saladin bars the road of Jerusalem to him. He obtains some successes, in particular in the coastal plain of Arsouf, in the north of Jaffa (September). Anxious to return to England, he insists to manage a fast agreement at Al-Adel. He claims Jerusalem, the territory in the west of the the Jordan and the true cross, that the Moslems took with Hattin. Saladin refuses in block, but opens the negotiations. Richard then proposes to give his sister, widow of the king of Sicily, in marriage with Al-Adel. He would give the grounds which he controls, of Acre to Ascalon, with his/her sister, while Saladin would yield its possessions of the littoral to his/her brother. The cross would be entrusted to them, and the prisoners of the two camps would be released. The agreement likes Al-Adel. Saladin accepts, conscious that it is about a trick. Its refusal would have displeased with Al-Adel, and causes the discord between the brothers. Richard, uncovered, must move back: his/her sister refuses to marry a Moslem!

Saladin, on its side, engages of the talks with Conrad de Montferrat which maintains the reports/ratios tended with Richard, suspecting it of wanting to deprive it of its possessions, and which goes until proposing to the sultan an alliance against Richard. He will be assassinated shortly after by ismaëliens of the sect of the Assassins. The negotiations between Richard and Saladin will still trail a year.

Some personalities died during the seat

• Etienne {{Ier}} of Sancerre.
• Thibaud V of Blois.
• Albéric Clement, first Marshal of France.
• Andre de Brienne.
• Raoul {{Ier}} of Coucy