James Rood Doolittle Sr. (January 3, 1815 – July 27, 1897) was an American lawyer, politician, and Wisconsin pioneer.

During his years in the Senate, he was a Republican and a strong supporter of Abraham Lincoln's administration during the American Civil War.

Along with his colleague, Jacob Collamer of Vermont, Doolittle represented the minority view for the Mason Report (June 1860), which was prepared by the Senate committee to investigate John Brown's raid on Harper's Ferry in October 1859.

During the Civil War, Doolittle supported many of Lincoln's policies, and he was active in representing Wisconsin's interests on Capitol Hill.

In the West, the committee split into subcommittees, which considered different regions with Doolittle participating in the inquiry into Native affairs in Kansas, the Indian Territory, and Colorado.

Doolittle was accused by The New York Times in 1872, while he was under consideration for appointment as Secretary of the Interior in the projected "reform cabinet" by Democratic presidential candidate Horace Greeley, of suppressing the report, as it contained information exposing the Native ring of fraudulent suppliers of goods to the Native tribes under treaty obligations.

He died of Bright's disease in Edgewood, Rhode Island in 1897,[7] and was interred in Mound Cemetery in Racine, Wisconsin.