The Indian Model O was a lightweight motorcycle made by the Hendee Manufacturing Company from 1917 to 1919.

The United States' entry into World War I caused Indian to shift manufacture to military motorcycles, and the low cost of the Ford Model T caused the market for lightweight motorcycles to collapse.

[2] In a layout similar to contemporary Douglas motorcycles from Great Britain, the Model O's flathead flat-twin engine was mounted with its cylinders along the line of the frame.

[1][2] The front suspension was initially a pivoting fork used on the Indian Single from 1906 to 1910 and on the Model K Featherweight.

[4] The appeal of lightweight motorcycles as transport was also eroded by the availability of mass-produced cars,[2] especially the Ford Model T, for which mass production began in 1913.