Delaware Route 30 (DE 30) is a state highway in Sussex County, Delaware. The route runs from an intersection with Bi-State Boulevard a short distance west of U.S. Route 13 (US 13) between Laurel and Delmar to DE 1 Business (DE 1 Bus.) southeast of Milford in the area of Lincoln City and Cedar Creek. The road runs east to Gumboro, where it turns north on the Millsboro Highway to Millsboro. Along this road, DE 30 shares concurrencies with DE 26, DE 54, and DE 24. From Millsboro, the route passes through Gravel Hill and to the west of Milton before reaching Milford. DE 30 has an alternate route, DE 30 Alternate (DE 30 Alt.), that was created by 1999 to connect the route with DE 1 by way of Johnson Road.

What is now DE 30 south of Gravel Hill was built as a state highway in various stages during the 1920s and 1930s. DE 30 was first designated by 1938 to connect DE 24 in Millsboro to DE 5 in Milton. The route was rerouted to end at DE 14 (now DE 1) south of Milford by 1971. DE 30 was extended southwest to Bi-State Boulevard by 1994 and its northern terminus was moved to DE 1 Business by way of a new road by 2003.

DE 30 runs begins at an intersection with Bi-State Boulevard in southwestern Sussex County, heading east on two-lane undivided Whitesville Road. A short distance later, the road crosses US 13, passing through a mix of farmland and woodland with some homes to the south of Trap Pond State Park. The route turns southeast and runs through more wooded areas with some fields and residences, curving to the east again. Farther east, DE 30 comes to an intersection with DE 26/DE 54.

At this point, DE 30 turns northeast to form a concurrency with DE 26/DE 54 on Millsboro Highway, passing through agricultural areas with some woods and homes. The road curves north and heads into the residential community Gumboro, where DE 54 heads to the east. DE 26/DE 30 continues past more homes, leaving Gumboro and heading back into areas of farms and forests with occasional residences. In Shaft Ox Corner, DE 26 splits to the east and DE 30 heads north to an intersection with DE 24.

Here, DE 24 turns north to join DE 30, with the road running northeast through agricultural and wooded areas. Farther northeast, residential development increases as the road heads into Millsboro. At this point, the road names becomes Laurel Road as it passes homes and reaches an intersection with US 113/DE 20. Past this intersection, DE 24/DE 30 turns north-northeast on Washington Street. The two routes split into a one-way pair following Main Street northbound and Washington Street southbound, crossing Norfolk Southern's Indian River Secondary railroad line. The one-way pair heads through the downtown area of Millsboro, rejoining along two-way Main Street and crossing Indian River to the east of Millsboro Pond. A short distance later, DE 24 and DE 30 split at an intersection.

Upon splitting from DE 24, DE 30 leaves Millsboro and heads north on Gravel Hill Road, passing to the east of Millsboro Pond. The road heads through a mix of farmland and woodland with some homes. In the community of Zoar, the route intersects DE 24 Alt. DE 30 runs through forested areas with some fields and residences, reaching the community of Gravel Hill. In Gravel Hill, the road crosses a Delaware Coast Line Railroad line and comes to an intersection with US 9/DE 404. From this point, the route runs through more rural areas, curving northwest before heading north again. DE 30 heads into agricultural areas and intersects DE 5 Alt., which serves as a western bypass of Milton for DE 5. Here, DE 5 Alt. turns north to form a concurrency with DE 30, with the road passing through farmland and woodland and crossing another Delaware Coast Line Railroad line. At an intersection with DE 16, DE 5 Alt. heads east along with that route and DE 30 continues north on Isaacs Road.

The route runs through farmland with some woods and homes, passing to the east of Reynolds Pond. DE 30 intersects Cedar Creek Road and turns northwest onto that road, curving north and back to the northwest as it heads through rural areas with some residential development. The road passes east of Swiggets Pond and intersects DE 30 Alt., which heads northeast to an intersection with DE 1. The route heads north-northwest and comes to an intersection with Wilkins Road, which intersects DE 1 a short distance to the northeast. Past this intersection, DE 30 turns northwest and passes between residential subdivisions to the southwest and DE 1 to the northeast, coming to its northern terminus at an intersection with DE 1 Bus. at the point that route merges into DE 1 at an interchange southeast of Milford.

DE 30 has an annual average daily traffic count ranging from a high of 20,273 vehicles at the northern edge of Millsboro to a low of 862 vehicles at the intersection with DE 26/DE 54. None of DE 30 is part of the National Highway System.

By 1920, what is now DE 30 existed as a state highway between Mission and Phillips Hill and was proposed as one between Phillips Hill and Millsboro, with the remainder of the route existing as a county road. The state highway between Phillips Hill and Millsboro was completed by 1924. The state highway portion of the present-day route was extended from Mission to Gumboro by 1925, with a section in the Gumboro area under proposal as a state highway. By 1931, the road was completed as a state highway between US 13 and Jones Branch and from James Branch to Gumboro. In addition, the state highway was completed from Millsboro to north of Gravel Hill as an unpaved road, with a portion north of Gravel Hill becoming a paved county road. The state highway between US 13 and Gumboro was fully complete by 1932. By 1936, the road between Millsboro and Gravel Hill was paved.

By 1938, DE 30 was designated to run from DE 24 in Millsboro north to DE 5 in Milton, following its current alignment to north of Gravel Hill and then running along Shingle Point Road north into Milton. A portion of current DE 30 south of the DE 16 intersection was paved by 1939. By 1952, the current route of DE 30 north of Gravel Hill was paved. DE 30 was rerouted to follow its present alignment north to DE 14 (now DE 1) south of Milford by 1971. By 1994, DE 30 was extended from Millsboro to its current terminus at Bi-State Boulevard. DE 30s northern terminus was moved to its current location at DE 1 Business by 2003 when a road connecting DE 30 to DE 1 Business was completed.

The entire route is in Sussex County.

Delaware Route 30 Alternate (DE 30 Alt.) is a 0.74 miles (1.19 km) alternate alignment of DE 30 south of the city of Milford in the Cedar Creek area. It runs from DE 30 northeast to DE 1 along Johnson Road, passing through a mix of farmland, woodland, and residential development. The route was created by 1999.