James Warner Ostrander (July 20, 1825 – December 21, 1913) was an American furniture manufacturer, banker, and Republican politician.

He served four non-consecutive terms (1873, 1875, 1879, 1882) in the Wisconsin State Assembly representing southern Jefferson County.

[2] He received a common school education, and came to Wisconsin in 1842, settling in Jefferson County, where he became a furniture manufacturer.

Caswell was not a candidate in 1874, and Ostrander returned, receiving 1,318 votes for P. N. Waterbury (running on the Reform Party ticket.

In October 1905, he was in correspondence with the "Maunesha Chapter" of the Daughters of the American Revolution, in Waterloo, from his home in Knoxville, Tennessee.