State Route 26 is a 96.7 mile-long state highway in southwestern Maine. It was first commissioned in 1925, as part of the New England road marking system. Route 26 in Maine, as well as New Hampshire and the short stub in Vermont, covers the route of the old New England Interstate Route 26. In the state of Maine, Route 26 runs from Portland in the southeast to the New Hampshire border near Upton, where it continues as New Hampshire Route 26.

Route 26 begins in Portland. State route logs show its southern terminus at State Route 77 in the western end of the city center at the intersection of Cumberland Avenue and State Street (southbound SR 77). From there it heads northeast along Cumberland Avenue, then turns north onto Washington Avenue. In the field, Route 26's southern end is signed at the intersection of Congress Street, Washington Avenue, and Mountfort Street in the eastern end of the city center one block south of the Cumberland Avenue intersection with Washington Avenue. From here, it follows Washington Avenue northward and joins with Interstate 295 and U.S. Route 1 over Tukey's Bridge, splitting off from that Interstate immediately on the other side of the bridge to continue northwest on Washington Avenue. Route 100 joins at Allen Avenue, and the combined Routes 26 and 100 immediately angle northward onto Auburn Street and continue together as far as the town of Gray.

From Portland, Route 26 generally parallels Interstate 95 (the Maine Turnpike) as far as Gray where it intersects with State Routes 115, 4, and US Route 202 and State Route 100 again splits off. The Turnpike begins to turn northeast at Gray, as does Route 100, but Route 26 continues north and then northwest. It passes the Grafton Notch before crossing into New Hampshire near Upton. In Maine, Route 26 passes through Cumberland, Androscoggin and Oxford Counties.

In 1988, the first attempt was made to modify the existing routing of a 5.25-mile stretch of Route 26 in the towns of Gray and New Gloucester. The existing roadway ran northward from Gray, hugging the Sabbathday Lake and then passed directly through the Shaker Village en route to New Gloucester, along current Shaker Road and Sabbathday Road. This, along with a second attempt in 1989, was rejected due to disagreement among the public and town officials of how the plan ought to be executed.

Plans were resurrected in 1996 with the formation of a Public Advisory Committee of thirteen members, composed of local citizens, local/regional government officials, and residents of the Shaker Village. Together, the PAC confirmed the existing deficiencies of the road, in particular a section locally known as the "Seven Deadly Curves." This section of the road was notorious for hazardous driving conditions due to lack of shoulders and small lane widths, numerous tight corners, and greatly varied speeds among vehicles traveling along the road. Other deficiencies were also addresses, such as hazards to pedestrians, truck noise and excessive vehicular traffic passing through the Village, and storm/lake water quality concerns.

Several new alignments were proposed for the project, the eventual winner being a southern bypass of the Sabbathday Lake area combined with a northern bypass of the Shaker Village. Two new segments of roadway were to be constructed as part of this new bypass. Environmental clearance was obtained in November 1998, with construction completed by the fall of 2004.

The bypass begins north of Gray, where Shaker Road (Route 26) meets Sabbathday Road. Route 26 splits left along a new alignment which runs for about 2 miles. Truck lanes were added on uphill climbs to improve traffic flow, and connecting roads from Route 26 provide access to the Sabbathday Lake area. Upon passing west of the lake, Route 26 rejoins its old alignment along former Sabbathday Road, which now dead-ends at its north end. After a mile or so, Route 26 once again splits left of Shaker Road, which dead-ends, passing just west of the Village for approximately 2 miles, with connecting roads providing access to the Village. Truck lanes are present on this section of road as well. North of the village, Route 26 returns to its old alignment approximately 1 mile south of its junction with Route 122 in Poland.

The Route 26 designation was removed from Shaker Road and Sabbathday Road, which now dead-end and do not directly connect to the bypass. The bypass is known as Maine Street and carries a speed limit of 55 MPH.

On November 16, 2006, a new 1.6-mile bypass, Route 26A, was completed and put into service to alleviate congestion in the center of Gray village where State Routes 26, 100, 115, 4, and U.S. Route 202 intersect. Much of the traffic congestion at this village center intersection was due to traffic on Route 26 being forced to pass through this central intersection when accessing and leaving the nearby I-95 Maine Turnpike Exit 63. One end of Route 26A begins at this intersection when it branches from Route 26 and runs west along U.S. Route 202 past the nearby turnpike exit before making a right-hand turn northward and running parallel to the turnpike on its opposite side until its other end where it rejoins Route 26 just south of the Gray-New Gloucester High School. In recognition of the heavy traffic flow of turnpike access, it is Route 26 which must yield at this junction, while traffic flow onto and from the new bypass Route 26A continues smoothly and unimpeded here.