Otto Axel Risum (February 24, 1835 – March 11, 1924) was an American farmer, merchant, and politician.

Born in Christiana, Norway, Risum emigrated to the United States in 1856 and eventually settled in Rock County, Wisconsin.

In 1873, Risum settled in Pulcifer, Shawano County, Wisconsin in the town of Green Valley.

Risum moved to Sawtelle, California to live in a warmer climate; he died there and was buried at the Los Angeles National Cemetery.

This article about a Republican Party member of the Wisconsin State Assembly born in the 1830s is a stub.