List of future Interstate Highways

In the United States, future Interstate Highways include proposals to establish new mainline (one- and two-digit) routes to the Interstate Highway System. Included in this article are auxiliary Interstate Highways (designated by three-digit numbers) in varying stages of planning and construction, and the planned expansion of existing primary Interstate Highways.

Congressionally designated future Interstates
Several Congressional High Priority Corridors have been designated as future parts of the Interstate Highway System by the Intermodal Surface Transportation Efficiency Act and amendments. By law, they will become interstates when built to Interstate standards and connected to other interstates.

Interstate 3
Interstate 3 is the proposed designation of an Interstate Highway Corridor under development in the Southeastern United States. It is planned to run from Savannah, Georgia, to Knoxville, Tennessee. Its number does not follow standard numbering conventions; under established numbering conventions, I-3 would normally run west of I-5 along the Pacific Coast. The unnumbered Interstate was established by the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) legislation that also provided for Interstate 14. The "Interstate 3" designation has not been officially accepted by American Association of State Highway and Transportation Officials (AASHTO) or the Federal Highway Administration (FHWA), but is being used by the Georgia Department of Transportation and others to identify the highway. The number comes from the 3rd Infantry Division, which is based in Georgia. The exact route has not been finalized.

Interstate 7 or 9
Interstate 7 or Interstate 9 has been proposed by Caltrans for State Route 99 in central California. It would go from the split with I-5 at Wheeler Ridge (Wheeler Ridge Interchange) north through Bakersfield and Fresno to Stockton, where the proposed route turns west via the SR 4 freeway to a terminus at I-5 in the central part of that city. An alternate proposed terminus is located at the I-5/US 50/Capital City Freeway junction in Sacramento, where the future Interstate, after continuing north from Stockton along Route 99, can turn west along the Capital City Freeway, already an Interstate route (unsigned I-305), to connect with I-5, which extends north toward Redding. This also serves as a connector to the existing northern portion of Highway 99. The future Interstate's prospects for development to appropriate standards are tied to the Caltrans "Route 99 Corridor Enhancement Master Plan"; this document posits that when and if Interstate status is conferred, the route will be designated either I-7 or I-9.

In August 2005, with the passage of that year's SAFETEA-LU federal transportation legislation, SR 99 from Wheeler Ridge to Stockton and beyond to Sacramento was designated as High Priority Corridor 54, the California Farm-to-Market Corridor; this legislation also designated that corridor as a future segment of the Interstate System.

Interstate 42
The Fixing America's Surface Transportation Act (FAST Act) added the US 70 corridor between Garner and Morehead City, North Carolina, to the Interstate system by defining it as, first, High Priority Corridor #82 and subsequently designating it as a future Interstate. The Regional Transportation Alliance expected this corridor to be called I-46 or another suitable designation. At a meeting in La Grange, North Carolina, on March 17, 2016, the Super 70 Corridor Commission recommended that the designation of I-50 be sought for the US 70 Interstate corridor. The rationale for the I-50 numerical selection was cited as a number not in conflict with either an existing Interstate designation or currently applied to a U.S. Highway within North Carolina. This recommendation was forwarded to NCDOT for submission to AASHTO.

For the AASHTO Special Committee on U.S. Route Numbering meeting in May 2016, NCDOT proposed I-36 for this route. However, AASHTO instead designated the route as I-42.

In March 2022, the Federal Highway Administration designated the 10 mi Clayton Bypass and the 22 mi Goldsboro Bypass, which have been built to Interstate Highway standards, formally as I-42 and NCDOT announced that the interstate would be signed by the end of the year. This, however, was delayed due to several projects on I-40 and the need for NCDOT to remove the North Carolina Highway 42 (NC 42) designation in Clayton to avoid confusion between that route and I-42. NCDOT plans to redesignate the Clayton portion of NC 42 to NC 36 with I-42 being signed within a year after the redesignation.

Interstate 905
Interstate 905 in California is proposed to replace California State Route 905.

Interstate 310 (Mississippi)
Interstate 310 is a proposed Interstate in Mississippi. Construction was supposed to begin in 2008 but never occurred. Much of the land clearing was done.

Interstate 422
Interstate 422 is a proposed beltway in Birmingham. Interstate 422 won't directly connect to I-22 so therefore a new connector known as Interstate 222 is proposed. A timeline for construction to begin has not been established.

Interstate 569
In April 2019, the Western Kentucky Parkway was originally proposed as Interstate 369 before being changed Interstate 569 in December 2019 as the Audubon Parkway was proposed to be Interstate 369.

Interstate 169 (Tennessee)
Interstate 169 is proposed to run along Tennessee State Route 22 from Union City to Martin.