55 Days at Peking is a 1963 American epic historical war film dramatizing the siege of the foreign legations' compounds in Beijing during the Boxer Uprising, which took place in China in the summer of 1900.

Starvation, widespread in China, is affecting more than 100 million peasants by the summer of 1900. Approximately a thousand foreigners from various western industrialized countries have exploited their positions inside Peking's legations, seeking control of the weakened nation. The Boxers oppose the westerners and the Christian religion and are planning to drive them out.

The turmoil in China worsens as the Boxer secret societies gain tacit approval from the Dowager Empress Cixi. With 13 of China's 18 provinces forced into territorial concessions by those colonial powers, frustration over foreign encroachment boils over when the Empress encourages the Boxers to attack all foreigners in Peking and the rest of China. When the Empress condones the assassination of the German ambassador and "suggests" that the foreigners leave, a violent siege of Peking's foreign legations district erupts. Peking's foreign embassies are gripped by terror, as the Boxers, supported by Imperial troops, set about killing Christians in an anti-western nationalistic fever.

The head of the US military garrison is US Marine Major Matt Lewis, loosely based on the real Major John Twiggs Myers, an experienced China hand who knows local conditions well. A love interest blossoms between him and Baroness Natasha Ivanova, a Russian aristocrat who, it is revealed, had an affair with a Chinese General, causing her Russian husband to commit suicide. The Russian Imperial Minister, who is Natasha's brother-in-law, has revoked her visa in an attempt to recover a valuable necklace. Although the Baroness tries leaving Peking as the siege begins, she is forced by events to return to Major Lewis and volunteers in the hospital, which is battered by the siege and is running out of supplies. To help the defenders, the Baroness exchanges her very valuable jeweled necklace for medical supplies and food, but she is wounded in the process and later dies.

Lewis leads the small contingent of 400 multinational soldiers and US Marines defending the compound. As the siege worsens, Maj. Lewis forms an alliance with the senior officer at the British Embassy, Sir Arthur Robertson, pending the arrival of a British-led relief force. After hearing that the force has been repulsed by Chinese forces, Maj. Lewis and Sir Arthur succeed in their mission to blow up a sizable Chinese arsenal.

As the foreign defenders conserve food and water, while trying to save hungry children, the Empress continues plotting with the Boxers by supplying aid from her Chinese troops. Eventually, a foreign relief force from the Eight-Nation Alliance arrives and defeats the Boxers. The troops reach Peking on the 55th day and, following the Battle of Peking, lift the siege of the foreign legations. Foreshadowing the demise of the Qing dynasty, rulers of China for the previous two and a half centuries, the Dowager Empress Cixi, alone in her throne room, having gambled her empire and lost, declares repeatedly to herself, "The dynasty is finished".

When the soldiers of the Eight-Nation Alliance have taken control of the city, after routing the Boxers and the remnants of the Imperial Army, Maj. Lewis assembles his men, having received new orders from his superiors to leave Peking. He stops and circles back to retrieve Teresa, the young, half-Chinese daughter of one of his Marine comrades who was killed during the 55-day siege. Aboard his horse, she and Maj. Lewis leave the city behind, followed by his column of marching Marines.