In the U.S. state of Colorado, U.S. Route 6 (US 6) is an east–west highway stretching from Utah to Nebraska. Much of the route overlaps other highways in Colorado, and as a result, much of US 6 is unsigned.

US 6 is concurrent with Interstate 70 for a significant portion of its length from the Utah state line to Denver. Within the city limits, US 6 follows Denver's 6th Avenue (known as "6th Avenue Freeway"). The highway then travels north briefly, and follows Interstate 76 for most of its length east of Denver. It is unsigned while it is overlapped. The highest altitude along US 6 is 11,990 feet (3,650 m) at Loveland Pass, where it crosses the Continental Divide. It continues down Clear Creek Valley until it reaches I-70, where it is briefly overlapped until I-70 leaves Clear Creek Valley. US 6 continues down Clear Creek and into Denver, where it turns into a freeway with 6 lanes. East of Denver, it continues east while joined with I-76 until it reaches Sterling, where it diverges from the interstate. The last town in Colorado it passes is Holyoke.

Colorado Highways: US 6