A memorial service is held at St. Paul's Cathedral in London for national hero T. E. Lawrence, known as 'Lawrence of Arabia', following his death in a motorcycle accident. Some of those who knew him are interviewed by a journalist on the cathedral steps, but no-one is able to give a straightforward opinion of the man.

In 1916, well-educated Lt. Lawrence is working as a cartographer for the British army in Cairo, but he feels out of place and longs to get into the desert. His chance comes when Mr. Dryden, of the Arab Bureau, arranges for him to be seconded to make contact with Prince Feisal and report on the progress of the Arab Revolt against the Turks.

Lawrence takes a Bedouin guide, whose desert survival tricks he determines to emulate. The guide is shot dead at a well by Sherif Ali, an Arab from a rival tribe. After a bitter altercation with Ali, Lawrence travels on alone, and meets with Colonel Brighton, who takes him to Feisal's army, which is under air bombardment from the Turks. Feisal is resigned to the inevitable absorption of his guerrilla forces into the regular British army, and believes that only a miracle will sustain the independent spirit of the Arab Revolt. Although instructed by Brighton to keep quiet, Lawrence speaks out, and impresses Feisal with his knowledge of, and obvious sympathy with, the Arab cause. Lawrence persuades Feisal to let him lead a small force across the notorious Nefud desert, in order to attack the Turkish port of Aqaba from the landward side - the garrison is too well-defended from the sea. Sherif Ali goes with them, as do two orphan outcasts, Farraj and Daud, who become Lawrence's servants.

After a gruelling journey the men reach the Devils' Anvil, where there is no protection from the relentless sun. One, Gasim, falls from his camel, but no-one misses him until the Anvil has been crossed. Alone and on foot, he faces certain death, but Lawrence insists on going back for him. When Lawrence brings Gasim back, alive and safe, Ali is so impressed by his courage that he gives the Englishman the white robes of a Sherif to wear instead of his army uniform. Lawrence encounters Auda Abu Tayi, the head of another Arab tribe, and persuades him to join forces for the attack on Aqaba.

The night before the attack, one Arab kills an Arab from another tribe. To prevent a blood feud, the culprit must be executed by a man from neither tribe. Lawrence agrees to do it, but is dismayed to see that the murderer is Gasim.

Aqaba is captured and Lawrence is hailed as a hero by the Arabs. When the radio transmitter is destroyed during the looting of the garrison, Lawrence takes Farraj and Daud with him across the Sinai desert to give the news to the British generals in Cairo. On the way, Daud falls into a quicksand and Lawrence cannot save him.

Exhausted and filthy, Lawrence and Farraj reach Cairo. When they go into the officers' bar, Lawrence's Arab robes excite much interest and some outrage. General Allenby is now in charge and Lawrence reports to him. He is promoted to Major, and Allenby agrees to give him arms and money if he will return to the Arabs and continue the fight against the Turks. Although Lawrence has been shaken by the realisation that he enjoys the act of killing, and he suspects that the French and British have designs on the Ottoman Empire themselves, he agrees.

Lawrence embarks upon a triumphant period of guerrilla warfare, blowing up the Turkish railway, hero-worshipped by his own men and made internationally famous by the dispatches of the American journalist, Jackson Bentley. Even a bullet in the shoulder from a wounded Turk does not slow him down. Most of the Arab army goes home when winter approaches, but Lawrence, Ali and a small group of followers continue to attack the railway. While carrying a detonator, Farraj falls and is terribly injured. Lawrence has to shoot him before the Turkish soldiers arrive.

On a scouting expedition with Ali in the Turkish-held town of Deraa, Lawrence is picked up the Turks and savagely beaten. His sense of his own invincibility shattered, Lawrence decides to give up his command and resume his life in the British army. However, Allenby once again sends him back to the desert. Lawrence now has a personal bodyguard made up of thieves and murderers, and his men follow him for money. On the way to take Damascus, they pass a village destroyed by the Turks. When the Arabs catch up with the Turkish column, Lawrence leads them in a savage and bloody attack.

The Arabs reach Damascus before the British, and Lawrence sets up an Arab Council to run the city, but it soon collapses into chaos under the strain of tribal divisions. The British take charge, Lawrence is promoted to Colonel and returns to England, while Feisal, Dryden and Allenby discuss the future of Arabia.