Pennsylvania Route 304 (PA 304) is an 13-mile (21 km) long state highway located in Union county in Pennsylvania. The western terminus is at PA 45 in Mifflinburg. The eastern terminus is at US 15 in Winfield.

PA 304 begins at an intersection with PA 45 in Mifflinburg, Union County, heading southeast on two-lane undivided South 4th Street. The road heads through residential areas before crossing into Limestone Township. In this area, the route heads south into open agricultural areas with a few homes, becoming an unnamed road. PA 304 curves southeast and reaches the residential community of Dice, continuing through a mix of farmland and woodland with a few residences. The road turns northeast through more open agricultural lands until it crosses into New Berlin. At this point, the name of the route becomes and it passes several homes, coming to an intersection with PA 204. After passing through more of the town, PA 304 heads back into agricultural areas with some residences and becomes County Line Road as it runs to the north of Penns Creek. The route becomes the border between Union Township, Union County to the north and Jackson Township, Snyder County to the south, with the creek turning south away from the road. PA 304 splits from County Line Road and fully enters Union Township as it passes through more rural areas on an unnamed road, running through Dry Valley Cross Roads. The road continues northeast through more farmland with occasional residences before coming to the community of Winfield. Here, PA 304 turns north and passes homes prior to ending at US 15.

The entire route is in Union County.

Pennsylvania Route 304 Truck is a 2-mile (3.2 km) long truck route in Mifflinburg, Union County, Pennsylvania. Narrow streets within the borough are avoided by this designation, and a complicated intersection with Pennsylvania Route 45, which does not contain turning lanes, is bypassed. The route is multiplexed with other highways for its entire length: it is cosigned with Truck Route 45 for its initial stretch, then corresponds with Pennsylvania Route 104 as it meets its terminus.