Bohemund I of Antioch (c. 1058 – March 3, 1111), prince of Taranto and afterwards prince of Antioch, was one of the leaders of the First Crusade.

Bohemund was the eldest son of Robert Guiscard, Duke of Apulia and Calabria, by his first marriage (which was later annulled) to Alberada of Buonalbergo. He was christened "Mark" but came to be known as Bohemund, after a legendary giant of that name.

He served under his father in the great attack on the Byzantine Empire (1080–1085), and commanded the Normans during Guiscard's absence (1082–1084), penetrating into Thessaly as far as Larissa, but being repulsed by Alexius I Comnenus. This early hostility to Alexius had a great influence in determining the course and policy of his reign from time of Bohemund (whom his father had destined for the throne of Constantinople) to King Roger.

When Robert Guiscard died in 1085, Bohemund inherited his father's Adriatic possessions, which were soon lost to the Greeks, while his younger half-brother Roger Borsa inherited Apulia and the Italian possessions. The war was finally resolved by the mediation of Pope Urban II and the award of Taranto and other possessions to Bohemund. Though Bohemund received a small principality (an allodial possession) for himself in the heel of southern Italy, as compensation from Sikelgaita after renouncing his rights to the Duchy, he sought a greater status for himself. The chronicler Romoald of Salerno said of Bohemund that "he was always seeking the impossible."

In 1096 Bohemund, along with his uncle Roger I of Sicily the great count of Sicily, was attacking Amalfi, which had revolted against Duke Roger, when bands of crusaders began to pass, on their way through Italy to Constantinople. The zeal of the crusader came upon Bohemund: it is possible however, that he saw in the First Crusade nothing more than a chance to carve for himself an eastern principality. Geoffrey Malaterra bluntly states that Bohemund took the Cross with the intention of plundering and conquering Greek lands.

He gathered a fine Norman army (perhaps the finest division in the crusading host), at the head of which he crossed the Adriatic Sea, and penetrated to Constantinople along the route he had tried to follow in 1082–1084. He was careful to observe a "correct" attitude towards Alexius, and when he arrived at Constantinople in April 1097 he did homage to the emperor. He may have negotiated with Alexius about a principality at Antioch; if he did so, he had little encouragement. From Constantinople to Antioch, Bohemund was the real leader of the First Crusade; and it says much for his leadership that the First Crusade succeeded in crossing Asia Minor, which the Crusade of 1101, the Second Crusade in 1147, and the Third Crusade in 1189 failed to accomplish.

The Emperor's daughter, Anna Comnena, leaves a good portrait of him in her Alexiad; she met him for the first time when she was fourteen, and was quite fascinated by him. She left no similar portrait of any other Crusader prince. Of Bohemund, she wrote:

"Now [Bohemund] was such as, to put it briefly, had never before been seen in the land of the Romans, be he either of the barbarians or of the Greeks (for he was a marvel for the eyes to behold, and his reputation was terrifying). Let me describe the barbarian's appearance more particularly -- he was so tall in stature that he overtopped the tallest by nearly one cubit, narrow in the waist and loins, with broad shoulders and a deep chest and powerful arms. And in the whole build of the body he was neither too slender nor overweighted with flesh, but perfectly proportioned and, one might say, built in conformity with the canon of Polycleitus... His skin all over his body was very white, and in his face the white was tempered with red. His hair was yellowish, but did not hang down to his waist like that of the other barbarians; for the man was not inordinately vain of his hair, but had it cut short to the ears. Whether his beard was reddish, or any other colour I cannot say, for the razor had passed over it very closely and left a surface smoother than chalk... His blue eyes indicated both a high spirit and dignity; and his nose and nostrils breathed in the air freely; his chest corresponded to his nostrils and by his nostrils...the breadth of his chest. For by his nostrils nature had given free passage for the high spirit which bubbled up from his heart. A certain charm hung about this man but was partly marred by a general air of the horrible... He was so made in mind and body that both courage and passion reared their crests within him and both inclined to war. His wit was manifold and crafty and able to find a way of escape in every emergency. In conversation he was well informed, and the answers he gave were quite irrefutable. This man who was of such a size and such a character was inferior to the Emperor alone in fortune and eloquence and in other gifts of nature."

A politique, Bohemund was resolved to engineer the enthusiasm of the crusaders to his own ends; and when his nephew Tancred left the main army at Heraclea, and attempted to establish a footing in Cilicia, the movement may have been already intended as a preparation for Bohemund's eastern principality. Bohemund was the first to get into position before Antioch (October 1097), and he took a great part in the siege of the city, beating off the Muslim attempts at relief from the east, and connecting the besiegers on the west with the port of St Simeon and the Genoese ships which lay there.

The capture of Antioch was due to his connection with Firuz, one of the commanders in the city; but he would not bring matters to an issue until the possession of the city was assured him (May 1098), under the terror of the approach of Kerbogha with a great army of relief, and with a reservation in favour of Alexius, if Alexius should fulfill his promise to aid the crusaders. But Bohemund was not secure in the possession of Antioch, even after its surrender and the defeat of Kerbogha; he had to make good his claims against Raymond of Toulouse, who championed the rights of Alexius. He obtained full possession in January 1099, and stayed in the neighbourhood of Antioch to secure his position, while the other crusaders moved southward to the capture of Jerusalem.

He came to Jerusalem at Christmas 1099, and had Dagobert of Pisa elected as Patriarch, perhaps in order to check the growth of a strong Lotharingian power in the city. It might seem that Bohemund was destined to found a great principality in Antioch, which would dwarf Jerusalem; he had a fine territory, a good strategic position and a strong army. But he had to face two great forces--the Byzantine Empire, which claimed the whole of his territories and was supported in its claim by Raymond of Toulouse, and the strong Muslim principalities in the north-east of Syria. Against these two forces he failed. In 1100 he was captured by Danishmend of Sivas, and he languished in prison until 1103. Tancred took his place; but meanwhile Raymond established himself with the aid of Alexius in Tripoli, and was able to check the expansion of Antioch to the south.

Ransomed in 1103 by the generosity of the Armenian prince Kogh Vasil, Bohemund made it his first object to attack the neighbouring Muslim powers in order to gain supplies. But in heading an attack on Harran, in 1104, he was severely defeated at Balak, near Rakka on the Euphrates (see Battle of Harran). The defeat was decisive; it made impossible the great eastern principality which Bohemund had contemplated. It was followed by a Greek attack on Cilicia; and despairing of his own resources, Bohemund returned to Europe for reinforcements in order to defend his position. His attractive personality won him the hand of Constance, the daughter of the French king, Philip I, and he collected a large army. Of this marriage wrote Abbot Suger:

"Bohemund came to France to seek by any means he could the hand of the Lord Louis' sister Constance, a young lady of excellent breeding, elegant appearance and beautiful face. So great was the reputation for valour of the French kingdom and of the Lord Louis that even the Saracens were terrified by the prospect of that marriage. She was not engaged since she had broken off her agreement to wed Hugh, count of Troyes, and wished to avoid another unsuitable match. The prince of Antioch was experienced and rich both in gifts and promises; he fully deserved the marriage, which was celebrated with great pomp by the bishop of Chartres in the presence of the king, the Lord Louis, and many archbishops, bishops and noblemen of the realm."

Dazzled by his success, Bohemund resolved to use his army not to defend Antioch against the Greeks, but to attack Alexius. He did so; but Alexius, aided by the Venetians, proved too strong, and Bohemund had to submit to a humiliating peace (the Treaty of Devol, 1108), by which he became the vassal of Alexius, consented to receive his pay, with the title of Sebastos, and promised to cede disputed territories and to admit a Greek patriarch into Antioch. Henceforth Bohemund was a broken man. He died without returning to the East, and was buried at Canosa in Apulia, in 1111.