New York State Route 305 (NY 305) is a north–south route in the Southern Tier that runs from the Pennsylvania state line in Cattaraugus County to the hamlet of Belfast in Allegany County, where it ends at NY 19. It intersects the Southern Tier Expressway (Interstate 86 or I-86 and NY 17) in Cuba. Route description NY 305 begins at the Pennsylvania state line as a continuation of PA 446 in the town of Portville. The designation proceeds northward as Portville-Eldred Road, paralleling the Allegheny River and ponds as a two-lane rural highway. After an intersection with Barbertown Road, NY 305 enters the hamlet of Carroll and passes several residences northward. The route crosses Oswayo Creek, intersecting with NY 417 (Portville-Ceres Road). NY 305 and NY 417 form a concurrency, crossing north through the hamlet of Toll Gate Corner as a two-lane residential street, entering the village of Portville. In Portville village, NY 305 turns to the northeast away from NY 417 at an intersection with Brooklyn Street. Turning north on Brooklyn, paralleling a long stretch of residences and crossing the former Bradford Division. Passing east of Chestnut Hill Cemetery, NY 305 leaves the village. In the town of Portville, NY 305 changes monikers to Portville-Obi Road, crossing into a two-lane rural highway. Paralleling Dodge Creek to the northeast, NY 305 crosses the county line from the town of Portville into the Allegany County town of Genesee, changing names to Obi Road. Continuing along Dodge Creek, NY 305 parallels several residences before bending northward into the hamlet of Obi in the town of Clarksville. In Obi, NY 305 intersects with County Route 5 (CR 5; Daggett Hollow Road) in the residential hamlet. Continuing northward, NY 305 enters the hamlet of West Clarksville, where the route becomes a two-lane residential street and an intersection with CR 40 (Jordan Hill Road). After leaving West Clarksville, NY 305 intersects with CR 1 (West Clarksville Road). NY 305 bends to the northwest, entering the town of Cuba, paralleling several mobile homes into the hamlet of South Cuba. In South Cuba, the route intersects with CR 6 before entering the village of Cuba. In Cuba, NY 305 becomes known as South Street, crossing the former Erie Railroad main line into the village. Continuing northward, NY 305 becomes a two-lane residential street. At the intersection with CR 20 (East Main Street), NY 305 changes names to