Places beginning with SO in Illinois, United States
- Sollitt
- Solomon
- Solon Mills
- Somerset
- Somerset, Township of
- Somer, Township of
- Somonauk
- Somonauk, Township of
- Songer, Township of
- Sonora (historical)
- Sonora, Township of
- Soperville
- Sorento
- South Addison
- South Barrington
- South Beloit
- South Branch Addition (subdivision)
- South Brighton (subdivision)
- South Chicago
- South Chicago Heights
- South Chicago Heights (subdivision)
- South Commons (subdivision)
- South Crest (subdivision)
- South Crouch, Township of
- South Danville
- South Deering
- South Dixon, Township of
- South Edgewater (subdivision)
- South Elgin
- South Elkhorn
- South Elmhurst
- South Englewood (subdivision)
- Southern Hills
- Southern View
- Southern View (subdivision)
- South Evanston
- South Fillmore, Township of
- South Flannigan, Township of
- South Fork, Township of
- South Freeport
- Southgate
- Southgate Estates Trailer Park (subdivision)
- South Grove, Township of
- South Harvey
- South Holland
- South Homer, Township of
- South Hurricane, Township of
- South Jacksonville
- South Kenwood (subdivision)
- Southland Acres (subdivision)
- Southlawn
- South Lawndale (subdivision)
- South Litchfield, Township of
- South Lockport
- South Lynn (subdivision)
- South Macon, Township of
- South Moline, Township of
- Southmoor
- Southmoor
- Southmore Heights (subdivision)
- South Muddy, Township of
- South Ottawa (historical)
- South Ottawa, Township of
- South Otter, Township of
- South Palmyra, Township of
- South Park
- South Park Terrace (subdivision)
- South Paw Paw
- South Pekin
- South Pole (subdivision)
- Southport
- South Rock Island, Township of
- South Rome
- South Ross, Township of
- South Roxana
- South Shore (subdivision)
- South Strasburg
- South Streator (subdivision)
- South Twigg, Township of
- Southwest, Township of
- South Wheatland, Township of
- South Wilmington