Delaware Route 141 (DE 141) is a state highway that serves as a western bypass of Wilmington, Delaware. Its southern terminus is at DE 9 and DE 273 in New Castle and its northern terminus is an interchange with U.S. Route 202 (US 202) and DE 261 in Fairfax. The route heads north from DE 9/DE 273 on four-lane divided Basin Road, becoming concurrent with US 202 at an interchange with US 13/US 40 and passes to the east of New Castle Airport. The highway becomes a freeway and reaches an interchange with Interstate 95 (I-95) and I-295, at which point US 202 splits from DE 141. The DE 141 freeway continues north through Newport to Prices Corner. Here, the freeway segment ends and DE 141 continues northeast as a surface road, with another brief freeway segment in Greenville. The route continues east across the Brandywine Creek on the Tyler McConnell Bridge and continues to US 202/DE 261.

What is now DE 141 between New Castle and Newport was originally designated as part of DE 41 in the 1930s. DE 141 was designated as a surface bypass of Wilmington between New Castle and Newport in the 1950s, running concurrent with DE 41 south of Newport. DE 41 was removed from DE 141 by 1971. In the 1960s, DE 141 was proposed to be upgraded to a freeway. Construction on the freeway segments between Newport and Prices Corner and in Greenville began in the 1970s and was completed around 1980. In the 1990s, several improvements were planned for DE 141 north of Prices Corner, including grade separation at Rockland Road completed in 1997 and relocation of the northern terminus to its current location at an interchange finished in 2007.

DE 141 begins at an intersection with DE 9 and DE 273 west of New Castle, where the road continues south as part of DE 9. From the southern terminus, DE 141 heads northwest on Basin Road, a four-lane divided highway. The road passes to the east of William Penn High School and continues through suburban areas of homes with some businesses. The route reaches a cloverleaf interchange with US 13/US 40 east of the New Castle Airport, at which point US 202 begins. From here, US 202 runs concurrently with DE 141, with the two routes passing between New Castle Airport to the west and residential neighborhoods to the east. The road passes between a Delaware Air National Guard station to the west and homes and commercial establishments to the east, coming to an intersection with the northern terminus of DE 37. Past this intersection, the median of US 202/DE 141 widens as the road intersects Airport Road.

After intersecting Airport Road, US 202/DE 141 becomes a freeway. The road comes to an interchange with I-95 and the southern terminus of I-295, at which point US 202 splits from DE 141 by continuing north along I-95. Past this interchange, DE 141 widens to six lanes and has a southbound exit and entrance for South James Street and Old Airport Road before the median narrows. The freeway comes to a viaduct that crosses the Christina River into Newport, where it passes near industrial areas and crosses over Amtrak's Northeast Corridor railroad line. In Newport, the route has an interchange with DE 4, at which point it narrows to four lanes and curves northwest with Newport Gap Pike serving as a frontage road on both sides. The freeway widens back to six lanes and heads into a below-grade alignment that passes through residential neighborhoods, leaving Newport.DE 141 reaches an interchange with DE 62, where the Newport Gap Pike frontage road ends and the freeway narrows to four lanes. Following this interchange, the six-lane freeway rises to ground level and passes to the west of the former Wilmington Assembly plant used by General Motors before coming to a bridge over CSX's Philadelphia Subdivision railroad line. The road passes through business areas and comes to an interchange with DE 2 and the southern terminus of DE 41 in Prices Corner.

After the DE 2/DE 41 interchange, the freeway section of DE 141 ends and the route heads northeast on at-grade Centre Road, a four-lane divided highway. The road passes through suburban residential neighborhoods and reaches an intersection with DE 34. Following this intersection, the route heads north between the Ferris School to the west and DuPont's Chestnut Run Plaza research facility to the east. DE 141 curves to the northeast and comes to an intersection with DE 48/DE 100. Here, DE 100 joins DE 141 and the road passes through industrial areas, curving north and becoming a freeway past the Barley Mill Road intersection. The freeway curves northeast and passes under an East Penn Railroad line before coming to a partial cloverleaf interchange with DE 52 in Greenville. Past this interchange, the road curves east and the freeway ends, with DE 100 splitting from DE 141 at an at-grade intersection by heading north on Montchanin Road.

Past this intersection, DE 141 continues east as four-lane divided Barley Mill Road, heading into wooded areas. The route becomes a two-lane undivided road as it passes to the south of the Hagley Museum and Library before crossing over the Brandywine Creek valley on the Tyler McConnell Bridge. Past the bridge, DE 141 turns northeast onto four-lane undivided Powder Mill Road, passing between woods to the northwest and the DuPont Experimental Station to the southeast. The road widens into a divided highway and runs between the Nemours Mansion and Gardens to the east and the DuPont Country Club to the northwest. The route passes to the west of the A.I. duPont Children's Hospital before coming to a bridge over Rockland Road. DE 141 makes a sharp curve to the southeast and comes to an intersection where Powder Mill Road splits to the east and Children's Drive heads southwest to provide access to Rockland Road and the children's hospital. The route continues southeast as it passes to the south of AstraZeneca's North American headquarters. DE 141 curves east and comes to its northern terminus at an interchange with US 202 in Fairfax, where the road continues northeast as DE 261.

In 2011, DE 141 had an annual average daily traffic count ranging from a high of 68,304 vehicles at the DE 4 interchange to a low of 14,639 vehicles at the University Avenue intersection between DE 9/DE 273 and US 13/US 40. None of DE 141 is part of the National Highway System.

By 1920, what would become DE 141 existed as an unimproved county road. The road between Prices Corner and Greenville was paved by 1924. A year later, the road between New Castle and Newport was upgraded to a state highway. When Delaware first designated its state highways by 1936, what is now DE 141 between New Castle and Newport was designated as part of DE 41, which continued northwest from Newport toward Hockessin and the Pennsylvania border. Also by this time, Powder Mill Road was paved. DE 141 was designated to run from DE 273 in New Castle to US 202 north of Wilmington by 1952, following DE 41 on Basin Road and James Street from New Castle and Newport, Centerville Road between Newport and Prices Corner, and Centre Road, Barley Mill Road, and Powder Mill Road between Prices Corner and US 202. By 1957, an interchange was built at US 13/US 40 and the route was widened into a divided highway between Faulkland Road and DE 48. DE 41 was removed from its concurrency with DE 141 by 1971.

In 1965, a $20 million ($150 million today) freeway was proposed along the DE 141 corridor between Newport and US 202 north of Wilmington, providing a bypass to the west of Wilmington. By 1971, the DE 141 freeway from Newport to Prices Corner was under design and the reconstruction of the route north of DE 48 began. The same year, a contract was awarded for construction of a grade separation of the Reading Railroad in Greenville. In 1973, work started to upgrade DE 141 between the Christina River in Newport and the Brandywine Creek near Greenville. A contract was awarded to construct the DE 141 freeway through Newport in 1974. The construction of interchanges in Prices Corner and at DE 52 were included in the Bond Bill in 1976. The DE 141 freeway from Newport to Prices Corner and in Greenville was completed by 1981. By 1985, US 202 was rerouted to follow DE 141 between US 13/US 40 and I-95. DE 100 was rerouted to follow DE 141 between DE 48 and Montchanin Road by 1990.

In 1992, an environmental assessment was approved for improving DE 141 between DE 2 and US 202. Among the improvements called for were a six-lane bridge over the Brandywine Creek replacing the existing two-lane bridge, a new bridge over Rockland Road, and a new interchange with US 202 and DE 261. Later in the year, the proposed bridge over the Brandywine Creek was scaled back to four lanes. In 1994, plans for the bridge over the Brandywine Creek and the US 202 interchange were placed on hold. Meanwhile, the bridge over Rockland Road was completed in 1997, with DE 141 being realigned between Rockland Road and US 202 and the intersection with Children's Drive improved. In the 2000s, the Blue Ball Construction Project relocated the northern terminus of DE 141 to an interchange with US 202 and DE 261 a short distance to the south of where Powder Mill Road intersects US 202. The project took place between 2002 and 2007 and cost $123 million. In 2007, construction began to upgrade the portion of DE 141 between DE 2 and DE 34 from a four-lane undivided road into a four-lane divided highway. Completion of the project was scheduled for 2010.

The entire route is in New Castle County.