The N3 is a highway in South Africa that forms a part of the National Road System, connecting Johannesburg and Durban, respectively South Africa's largest and second-largest cities. Johannesburg is the financial and commercial heartland of South Africa, while Durban is South Africa's key port and one of the busiest ports in the Southern Hemisphere and is also a holiday destination. Durban is the port through which Johannesburg imports and exports most of its goods. As a result, the N3 is a very busy highway and has a high volume of traffic, even though the distance covered is just short of 600 kilometres.

Following the opening of a new freeway section in December 2001 between Heidelberg and Villiers, the road is now dual carriageway for its entire route between the two cities. The section between Johannesburg and Villiers along the Vaal River is divided dual carriageway, or in other words, a freeway. Between Villiers and the outskirts of Ladysmith, the road is undivided dual carriageway. Between Ladysmith and Durban, the road again becomes a divided dual carriageway.

The N3 is divided into 12 sections, starting with section 1 in Durban and ending with section 12 in Johannesburg. Between the two cities, the route covers the following towns and cities: Heidelberg, Villiers, Warden, Harrismith, Van Reenen , Estcourt, Mooi River , Howick, and Pietermaritzburg.

From Johannesburg, the route officially starts at the Buccleuch Interchange which is the point at which the N3, N1, and M1 freeways converge. After winding its way down the eastern side of Johannesburg as part of the city's N3 Eastern Bypass, it then moves away from the city down towards Heidelberg. Further along, the route passes through the small town of Harrismith along a bypass in the foothills of the Drakensberg mountain range. From there, it takes its most dramatic drop down through Van Reenen's Pass into the rolling hills of the KwaZulu-Natal Midlands.

The route becomes rather picturesque as it continues on its journey down to Durban, passing through dairy farmland around Mooi River, and the Midmar Dam near Howick. At Pietermaritzburg, the road makes another dramatic drop down into the city as it passes Town Hill, along the city's bypass. From there, the road makes an 80 kilometre line for the coast, passing into Durban through the outskirts of Pinetown and Westville. Connecting with the N2 Durban Ring Road at the Westville Four-Level Interchange, the road then spills into the Durban Central Business District at its end. The road is tolled for most of its length.

There are plans to re-route one section between the Tugela Toll Plaza near Ladysmith, and the start of the tolled section near Warden. This would see a new freeway winding its way through the De Beer's Pass , as opposed to Van Reenen, which would cut another 13 kilometres off the route. This has caused a huge outcry among residents of Harrismith and Van Reenen, who rely on passing traffic to sustain businesses such as restaurants, petrol stations, and holiday rest places. But proponents of the new road argue that the existing Van Reenen's Pass is too steep for heavy trucks and does not meet the maximum gradient of 1:7 for an officially declared national road.