John Isaac Cox (1857–1946) was Governor of Tennessee from 1905 to 1907.

Cox was born in Sullivan County, Tennessee, and was the son of a Confederate soldier, which was less common in East Tennessee than in the rest of the state, as East Tennessee was one of the Southern strongholds of pro-Union sentiment during the Civil War. Cox became affiliated with the Democratic Party, which was also less popular in the eastern part of the state than elsewhere; this also relates back to the Civil War legacy. However, the Democratic Party has traditionally been stonger in Sullivan County than elsewhere in the northeastern part of the state.

Cox became a practicing attorney in 1885 and was subsequently elected county judge of Sullivan County. (This position in Tennessee at that time combined minor judicial functions with the position of chief executive officer of the county, a position currently referred to in Tennessee as "county mayor".) He later served as district attorney and was elected to the Tennessee House of Representatives in 1892, serving until 1894. He was then elected to the Tennessee State Senate in 1900 and was serving as Speaker of that body, which in Tennessee is the governor's designated successor (and in recognition of this fact now carries the additional title of Lieutenant Governor of Tennessee), when, on March 21, 1905, Governor James B. Frazier arranged for himself to be appointed to the unexpired United States Senate term of Senator William B. Bate, who had died in office, and then subsequently resigned as governor. This made Cox governor of Tennessee.

The current flag of Tennessee, designed by LeRoy Reeves, was adopted during Governor Cox's term. Prison riots, which had plagued Tennessee for decades during this era, flared again. A major effort to eradicate yellow fever, which had long plagued particularly the swampy western part of the state, was undertaken. Cox chose not to run for another term as governor, but instead for his former position as a state senator. He won election to that office two subsequent times, serving from 1907 to 1911. He later served another term as a state representative from 1913 until 1915, and was the postmaster of Bristol, Tennessee from 1914 to 1922, when he retired from public service.