U.S. Route 95 is a north–south U.S. highway in the western United States. Unlike many other US highways, it has not seen deletion or replacement on most of its length by an encroaching Interstate highway corridor, due to its mostly rural course. Because of this, it still runs from border to border and is a primary north–south highway in both Nevada and Idaho.

As of 2010, the highway's northern terminus is in Boundary County, Idaho, at the Canadian border crossing of Eastport, where it continues north as BC 95. Its southern terminus is in San Luis, Arizona, on the Mexican border, where a short spur leads to Mexican Federal Highway 2 at San Luis Río Colorado, Sonora.

US 95 begins in the United States at the border with Mexico at Mexico's Federal Route 2. It then follows the Colorado River northward to San Luis and on to Yuma, where it goes through town and crosses I-8. As it leaves Yuma, US 95 is an undivided two-lane highway which passes through the U.S. Army's Yuma Proving Ground.

It then travels northward between the proving ground to the west and the Kofa National Wildlife Refuge to the east until Quartzsite. Here it merges with I-10 and runs concurrent, heading westward for 17 miles (27 km) until the Colorado River, where it enters California, just shy of Blythe.

In all, US 95 spends 123.16 miles (198.21 km) in Arizona.

U.S. 95 enters California at Blythe through a concurrency with Interstate 10. It travels largely parallel to the west bank of the Colorado River until it joins Interstate 40 in Needles. The route then travels north from Goffs to the Nevada line. The total distance in California is about 130 miles.

US 95 in Nevada is a divided highway between the Laughlin junction and Boulder City. Upon entering the Las Vegas area, the highway becomes a multi-lane divided freeway and is concurrent with I-515 and US 93 between Henderson and Downtown Las Vegas. After crossing I-15, the highway continues as a freeway for several miles until again becoming a divided highway outside the Las Vegas urban area.

Shortly after entering Nye County, US 95 becomes an undivided two-lane highway, as it meanders northwestward through the state, roughly paralleling the California border. The highway is concurrent with US 6 for several miles north of Tonopah and concurrent with I-80 for 93 miles (150 km), from Exit 83 west of Lovelock to Exit 176 at Winnemucca. It then heads north to the border with Oregon at McDermitt, a distance of 73 miles (117 km).

In Oregon, US 95 is an undivided two-lane highway in the sparsely populated high desert in the southeastern corner of the state, running completely in rural Malheur County. From the Nevada state line at McDermitt, the highway heads north and gradually climbs to its crest at Blue Mountain Pass, at an elevation of 5293 feet (1613 m) above sea level. US 95 descends to Basque Station (webcam) and Burns Junction at 3960 feet (1207 m), then eastward down to Rome (3390 ft, 1033 m) and up to Jordan Valley (4389', 1338 m) (webcam). The highway heads north-northeastward to the Idaho state line, entering southwest of Marsing in Owyhee County.

US 95 is designated the I.O.N. Highway No. 456 (see Oregon highways and routes), with the I.O.N. for Idaho-Oregon-Nevada. This section of highway is a primary commercial route between Boise and northern California, connecting to Interstate 80 at Winnemucca, Nevada. US 95 crosses into the Mountain Time Zone approximately 35 miles (56 km) north of Nevada.

US 95 is an undivided two lane highway during most of its length in Idaho, which is over 538 miles (866 km). The state is widening US 95 to a four lane divided highway from the Oregon state line to the Canadian border at Eastport.

US 95 enters Idaho from Oregon in Owyhee County, about 50 miles (80 km) southwest of Boise. It passes through Homedale and crosses the Snake River before a junction with concurrent US 20 and US 26, which run together for eight miles (13 km). As it proceeds north, US 95 crosses I-84 and US 30 before going through the Payette National Forest. Immediately after Riggins, the highway re-enters the Pacific Time Zone as it crosses the Salmon River. US 95 follows the descending river, then climbs over White Bird Hill to the Camas Prairie, then descends the Lapwai Canyon to the Clearwater River.

US 95 becomes a four lane divided highway after crossing the river east of Lewiston; it runs concurrent with US 12 for several miles. The highways split as US 12 continues west to Lewiston, and US 95 turns northwest and climbs a steep grade up to the rolling Palouse. At a junction with US 195, US 95 proceeds north to Moscow as a recently completed divided highway. It becomes an undivided highway in Moscow and continues north to Coeur d'Alene, crossing I-90. US 95 goes north to Sandpoint, where it joins with US 2, after which the highways run concurrent until after Bonners Ferry, where US 2 heads east to Montana and US 95 continues north to Canada, meeting BC 95 at the border.

U.S. Route 95 was one of the original U.S. highways proposed in the 1925 Bureau of Public Roads numbering plan. Under the original proposal, the highway would only exist in Idaho, from Payette to the Canadian border north of Eastport. When the plan was adopted by the American Association of State Highway Officials in November 1926, the route of US 95 had been approved south to Weiser, still existing solely in Idaho. A proposal to extend US 95 south to Winnemucca, Nevada was considered by AASHO in 1937; however, action was deferred due to sections in Oregon that were incomplete. AASHO reconsidered the idea at its meeting on June 28, 1939, as part of a larger plan to extend the highway south to Blythe, California. This plan was adopted at that meeting and became effective on January 1, 1940.

North of Lewiston, Idaho, US 95 entered Washington for 0.54 miles (0.87 km), partially concurrent with U.S. Route 195. The route was moved to a new 4-laned divided road that bypassed Washington in the 1970s.

The route is now U.S. Route 195 Spur.

Between 2009-2010, the Arizona Department Of Transportation has decided to make the beginning stretch of US 95 between Yuma and Parker four lanes instead of the current two-lane configuration to make it safer, quicker, and easier to travel.

In April 2005, the Idaho legislature approved a bill to widen the entire highway from two lanes to four lanes for the entire route starting at the US-Canada port of entry in Eastport, and ending at the Oregon border in remote Owyhee County. The contract for the project was awarded to Washington Group International and CH2M Hill. The contract is worth more than $1.2 billion, and is slated to last for more than six years, cover 13 major reconstruction projects, affecting over 250 miles (402 km) of the highway's nearly 460 miles (740 km) in the state.

The major factors in the reconstruction are due to the fact that US 95 is the only route that runs from north to south in western Idaho, starting at Eastport in the north and ending in remote Owyhee County; as well as safety concerns because there have been numerous accidents and fatalities on the narrow and very dangerous curves. This change started with the re-construction and improvements made to White Bird Hill. Major projects have been undertaken including on the Coeur d'Alene Indian Reservation.

The first stage was completed in August 2005 from just south of Coeur d'Alene to Fighting Creek Road, and is an upgraded four-lane highway for approximately ten miles (16 km). The second stage, from Fighting Creek Road to Lake Creek on the Coeur d'Alene Indian Reservation, was completed in late July-early August 2006 and upgraded a seven-mile (11 km) stretch of the highway. The third stage, from Lake Creek to Worley, started mid-to-late 2006 and was completed in 2008. This section is significant, as it is on the Coeur d'Alene Indian Reservation. The "new" highway bypasses the Coeur d'Alene Casino, the largest business on the reservation, with the old highway becoming an alternate route that will connect the highway to the casino and the more remote regions of the reservation. This project improved a 20-mile (32 km) stretch of highway and shortened the length of the highway by about 20 miles (32 km).

Also, a nearly 20-mile (32 km) stretch was completed in 2007 from just north of Lewiston to 6 miles (10 km) south of Moscow.