Computing •
Swiss Informatics Society, a Swiss organization of computer science educators, researchers, and professionals •
The SI, a former name of the American defense contractor Vencore
Education •
St. Ignatius College Preparatory, a Jesuit high school in San Francisco, California, US •
Silay Institute, a private college in the Philippines
Government • Si, a
South Korean administrative unit •
Survey of India, an Indian government agency responsible for managing geographical information •
Swedish Institute (
Svenska institutet), a Swedish government agency which promotes Sweden abroad
Politics •
Sarekat Islam, a socio-political organization in Indonesia under Dutch colonial rule •
Catalan Solidarity for Independence, a Catalan political party •
Situationist International, an organization of social revolutionaries •
Socialist International, a worldwide organization of political parties •
Solidarity and Equality, an Argentine political party (Spanish:
Solidaridad e Igualdad)
Transportation •
Blue Islands (IATA airline code, SI) •
Skynet Airlines (IATA airline code SI, ceased operating 2004) •
Spokane International Railroad (reporting mark SI), a former railway in Washington, US
Other enterprises and organizations •
Samahang Ilokano, a fraternity/sorority based in the Philippines •
SÍ Sørvágur, a Faroese sports association •
Society of Indexers, a professional society based in the UK •
Sports Interactive, a British computer games development company ==People with the name==