The list of Interstate Highways in Pennsylvania encompasses 23 Interstate Highways—12 primary routes and 11 auxiliary routes—which exist entirely or partially in the U.S. state of Pennsylvania. In Pennsylvania, Interstate highways are maintained by the Pennsylvania Department of Transportation (PennDOT). Interstate highways make up three percent of all roadway lane miles in Pennsylvania and have a combined length of 1,953 mi (3,143 km) within the state. Twenty-four percent of all vehicle traffic is on the Interstate system.
Interstate 78 begins at I-81 five miles (8 km) west of Fredericksburg in Lebanon County. It is multiplexed with US 22 as the William Penn Highway from Exit 8 in Fredericksburg to Exit 51 in Allentown. The highway was briefly designated as I-80N from 1957 to 1958. I-78 exits Pennsylvania and enters New Jersey via the Interstate 78 Toll Bridge in Easton.
Interstate 79 enters Pennsylvania at the West Virginia state line one mile (1.6 km) south of Mount Morris in Greene County. The highway travels north to Erie, bypassing Pittsburgh. I-79 is named to Raymond P. Shafer Highway for its entire length. Between Exits 65 and 68, I-79 is part of the Yellow Belt of the Pittsburgh Belt System. The only multiplex on the route is with I-70 in Washington from Exit 34 to Exit 38. The interstate ends at PA 5/PA 290 and the Bayfront Parkway at Exit 183 in Erie.
Interstate 83 enters Pennsylvania at the Maryland border four miles (6 km) south of Shrewsbury in York County and heads north for York and Harrisburg. The road is known as the Veterans of Foreign Wars of the United States Memorial Highway as well as the Harrisburg-York-Baltimore Expressway. While in Harrisburg it is also known as the Capital Beltway. I-83 ends at I-81 at Exit 70 in Harrisburg.
Interstate 84 begins at I-81 at Exit 187 in Scranton and heads east to the New York state line over the Delaware River in Matamoras. Originally, plans were made to build the interstate to cross extreme northern Pennsylvania, but the mountains proved to be too big of a challenge. Scranton is the only major city on the route.
Interstate 90, known as the AMVETS Memorial Highway, enters Pennsylvania from Ohio three miles (5 km) west of Springfield and exits at the New York border two miles (3 km) east of North East. The highway crosses Erie County along the lake, bypassing the city of Erie.
Interstate 99 is an incomplete highway in central Pennsylvania. It is known as the Appalachian Thruway and is located entirely within the state. It begins at Business US 220 in Bedford, Bedford County. It continues north through Altoona and State College before ending at a non-freeway interchange with I-80 near Bellefonte. The entirety of the current route is multiplexed with US 220. It will eventually extend southward to the Maryland border along the current alignment of US 220, and northward along US 220 to Williamsport, and along US 15 from there to the New York border to Interstate 86 in Painted Post, New York.
Interstate 476, the Blue Route, begins at I-95 Exit 7 in Chester in Delaware County. At Exit 20, the highway becomes the PA Turnpike Northeast Extension. The highway travels north around Philadelphia and through Montgomery, Bucks, Lehigh, Carbon and Luzerne counties. It passes Allentown before it ends in Clarks Summit near Scranton at I-81/US 6/US 11. It is the longest Auxiliary Interstate in Pennsylvania and the United States.
Interstate 576 will begin at the Pittsburgh International Airport and will travel in an east-west direction along the Southern Beltway route in Pittsburgh, terminating at the Mon-Fayette Expressway (Pennsylvania Route 43). Route is currently designated as Pennsylvania Route 576, but will most likely be upgraded to Interstate Highway status after the Southern Beltway is completed.
Interstate 380, known as the Scranton-Dunmore Expressway in Scranton, begins at I-80 at Exit 293 in Crescent Lake, Monroe County. It ends at I-81 at Exit 187 in Scranton. The Interstate gives Scranton direct access to the Pocono Mountains.
Interstate 195 will begin at the I-95/I-276/PA Turnpike interchange (currently under construction) and will utilize the existing I-95 right-of-way between the interchange and the Scudder Falls Bridge to New Jersey.