The REO Motor Car Company was a Lansing, Michigan based company that produced automobiles and trucks from 1905 to 1975. At one point the company also manufactured buses on its truck platforms.

Originally the company was to be called "R. E. Olds Motor Car Company," but the owner of Olds' previous company, then called Olds Motor Works, objected and threatened legal action on the grounds of likely confusion of names by consumers. Olds then changed the name to his initials.

Olds Motor Works soon adopted the popular name of its vehicles, Oldsmobile (which, along with Buick and Cadillac, became founding divisions of General Motors Corporation).

The company's name was spelled alternately in all capitals REO or with only an initial capital as Reo, and the company's own literature was inconsistent in this regard, with early advertising using all capitals and later advertising using the "Reo" capitalization. The pronunciation, however, was as a single word. Lansing is home to the R. E. Olds Transportation Museum.