Ohio Scientific Inc. (also known as Ohio Scientific Instruments) was a United States computer company that built and marketed computers from the late 1970s to the early 1980s. The company was founded by Mike and Charity Cheiky in 1975 in Hiram, Ohio.

One of their first products, launched in 1978 was the OSI Model 500 system, a very simple single board computer based on the MOS Technology 6502 microprocessor, but lacking a Video Display Controller. It needed an external video terminal such as the VT100, or the CT-64 terminal system from SWTPC, to create a useful system. Their later products were also 6502-based, the Superboard II, Challenger 1P, Challenger 4P and Challenger 8P, introduced in 1979 and discontinued in 1981.

Original Ohio Scientific motherboard designs used 7400-series transistor-transistor logic TTL chips. Instead of using a floppy disk controller IC, they used the Motorola 6850 ACIA serial-port UART chip, which made their 8 and 5 inch floppies unreadable on any other system.