John Robert Dinsmore Sr. (January 18, 1855 - April 27, 1900) was an American lawyer and Democratic politician from Macon, Mississippi.

[7] In 1899, Dinsmore was elected to represent the 16th District in the Mississippi State Senate for the 1900–1904 term.

[1][9] While still in office, Dinsmore died of apoplexy at his home in Macon, Mississippi, on April 27, 1900.

[5] In the 1902 session, he was succeeded in the 16th District by A. T. Dent, and as president pro tempore by William Gwin Kiger.

[10][12] They also had a son, John Robert Jr. (born July 4, 1892), who married Mary Chastellette Avery on September 22, 1917, and served as a Captain in the U.S. Infantry during World War I and was elected to the Mississippi House himself in 1919 for the 1920–1924 term.