Jefferson State may refer to:
- Jefferson (Pacific state) - the proposed fifty first state of the United States ongoing local political support since 1941. The proposed state would span southern Oregon and the northernmost counties of northern California. The proposed new conservative state would be formed by separating/seceding Oregon and California.
- Jefferson (Southern U.S. state) - 1870, 1915 and 1921 proposed U.S. state created by dividing Texas. It would include mostly west Texas.
- Jefferson (Mountain state) - 1859 proposed U.S. state from the former "Jefferson Territory". This included land that was part of the Utah Territory, Nebraska Territory, New Mexico Territory, Washington Territory and Kansas Territory. In 1861, much of that proposed state became the new state of Colorado.