The Dartford Crossing joins Dartford and Thurrock across the River Thames, forming part of London's orbital M25 motorway and the furthest-downstream road crossing of the Thames. It consists of two tunnels under the river, normally used for northbound traffic, and the Queen Elizabeth II Bridge, used for southbound traffic.

The bridge, completed in 1991, is a four-lane cable-stayed bridge, designed by Dr. Ing Hellmut Homberg and Partner and Kvaerner Technology Limited. It was built by a joint venture between Kvaerner Construction Limited and Cleveland Bridge & Engineering Company. When it was opened, the bridge was Europe's largest cable-supported bridge.

The central span is 450 m (1,476 ft) long and is suspended 65 m (213 ft) above the Thames to accommodate ocean-going cruise liners. 84 metre high steel pylons ayre located above 53 metre high concrete piers giving the bridge a total height of 137 metres. From these, the road deck is suspended by cables. The approach viaducts on the Essex side measure 1,052 m (3,451 ft) and 1,008 m (3,307 ft) on the Kent side, giving a total length of 2,872 m (9,423 ft). It has an expected life span of 120 years.

It is a toll bridge and accommodates four lanes of southbound traffic from the M25. When closed, owing to high winds for example, one of the two adjacent tunnels is used instead. With daily traffic flows of 150,000 vehicles the crossing suffers regular traffic congestion.

When built, the Queen Elizabeth II bridge was only the second bridge on the River Thames east (downstream) of London Bridge constructed in over a thousand years, and it is currently the only bridge east of Tower Bridge (the proposed Thames Gateway Bridge would be another). The historic reason for this is that bridges prohibited tall ships and other large ships from reaching the Pool of London, which has led to the building of numerous tunnels instead. High Speed 1 passes under the bridge (between the bridge supports) on the north (Essex) side and tunnels under the river just east of the bridge. The rail line passes over the exit ramps of both of the road tunnels.