SIM is an international, interdenominational Evangelical Christian mission organization. It was established in 1893 by its three founders, Walter Gowans and Rowland Bingham of Canada and Thomas Kent of the United States.

The initials originally stood for "Soudan Interior Mission," Soudan being an older spelling of the Sudan region of West Africa. After various name changes and mergers, the mission simply goes by "SIM" today. In French-speaking countries it is known as "Société Internationale Missionnaire." SIM is also a member of the Forum of Bible Agencies International.

SIM was founded in 1893, although the earliest elements of it were founded in 1860 with the British Syrian Schools Association in the Middle East. It is built up of a succession of partnerships and mergers.

In 1893 Walter Gowans, Rowland Bingham and Thomas Kent landed in Lagos, Nigeria. Their aim was to evangelize the "Soudan" region of Africa through the organization of the "Soudan Interior Mission." Gowans and Kent traveled to what is now Northern Nigeria with a Kru guide, Tom Coffee, but the two died of malaria. Bingham survived and returned to his home in Canada.

Bingham reorganized the mission in 1898 as the "African Industrial Mission," with a hope to be self-supporting through the production and trade of cotton. In 1900, Bingham made a second attempt to establish a base in Africa but came down with fever and returned home. A third attempt in 1902 succeeded, which finally established a base 500 miles inland in Patigi, Nigeria. In 1906, the mission was once renamed "Sudan Interior Mission."

After the initial base was set up, the mission branched out into other countries in West Africa, and then in the 1920s, to East Africa. Until 1998, SIM worked in Benin, Burkina Faso, Central African Republic, Ivory Coast, Eritrea, Ethiopia, Ghana, Guinea, Kenya, Liberia, Malawi, Niger, Nigeria, Senegal, South Africa, Sudan and Togo.

In 1907, George Allan and his wife Mary, née Stirling, from New Zealand, initiated the Bolivian Indian Mission (BIM), later known as Andes Evangelical Mission (AEM). Initially, the headquarters was located in San Pedro de Buena Vista before being transferred to the more accessible Cochabamba. Whereas the mission activities were relatively straightforward among the Quechua on the (highland) Altiplano, the real challenge began when the BIM reached out to the naked tribes of the inhospitable lowland Beni region. Here, in 1923, while exploring the area prior to establishing a mission station, BIM-founder Allan narrowly escaped death from malaria, but young fellow missionary Henry C. Webendorfer succumbed to the disease. According to Allan's daughter Margarita Allan Hudspith, William Fulton McKay, Frank Chaplin and Charles Trotman were among the missionary pioneers in the rainforests of Bolivia.

AEM joined SIM in 1982, and the work of SIM expanded to a new continent, South America.