The D Line is a light rail line which is part of the rail system operated by the Regional Transportation District in the Denver–Aurora Metropolitan Area in Colorado.

The D Line's northern terminus is in downtown Denver, at 19th Street.

The 2004 voter approved FasTracks plan will add 2.5 mi (4.02 km) to the D Line.

This will bring the line's southern terminus to a new station with 1,000 parking spots at C-470 and Lucent Boulevard in Highlands Ranch.

Additionally, the 2010 evaluation suggested an intermediate station at C-470 and South Erickson Boulevard, which was not a part of the original FasTracks plan.