William Booth (10 April 1829 – 20 August 1912) was an English Methodist preacher who, along with his wife, Catherine, founded the Salvation Army and became its first General (1878–1912). The Christian movement with a quasi-military structure and government was founded in 1865 and has spread from London to many parts of the world. It is known for being one of the largest distributors of humanitarian aid.

Booth, the son of a speculative builder, was apprenticed as a pawnbroker's assistant as a child. At 15, he experienced a religious conversion and became a revivalist preacher. In 1849, he moved to London to work in a pawnbroker's shop in Walworth, detesting the business but forced by necessity to earn money for his family. During this time, he met Catherine Mumford, his future wife and lifelong companion. By 1852, he had become a regular preacher for the Methodist New Connexion and married her in 1855. After nine years of ministry, Booth left the New Connexion and began his career as an independent evangelist.

Booth held a simple belief that eternal punishment awaited the unconverted, coupled with a deep pity for the marginalized and an aversion to dirt, misery, and suffering. In 1864, Booth moved to London and continued his services in tents and open-air venues, founding the Christian Mission in Whitechapel, which evolved into the Salvation Army in 1878. Booth modeled his "Orders and Regulations" on those of the British army. His early "campaigns" met with violent opposition, with an "Army of Skeletons" organized to disrupt meetings, and for many years, Booth's followers were fined and imprisoned for disturbing the peace. After 1889, such disturbances were rarely heard of.

The army's operations expanded to the United States in 1880, Australia in 1881, and later to continental Europe, India, Ceylon (now Sri Lanka), and other locations. General Booth himself was an indefatigable traveler, organizer, and speaker.

In 1890, General Booth published In Darkest England, and the Way Out, with the help of William Thomas Stead. The book proposed remedies for poverty and vice through various aid programs for society's most needy and distressed. The public support for the program was significant; funds were generously subscribed, and much of the plan was implemented. The opposition and ridicule that Booth's work faced for many years gradually gave way to widespread sympathy by the end of the 19th century as its results became more apparent. The active encouragement of King Edward VII, who insisted on Booth's official invitation to the coronation ceremony in 1902, marked a change in public perception. By 1905, Booth was welcomed with great distinction by mayors and corporations of many cities during his tours in England. The fiery old man had become a major figure in English life.