Deerfoot Trail is a 46.4-kilometre (28.8 mi) freeway segment of Highway 2 in Calgary, Alberta, Canada. It stretches the entire length of the city from south to north and links suburbs to downtown via Memorial Drive and 17 Avenue SE. The freeway begins south of Calgary where it splits from Macleod Trail, crosses the Bow River into city limits, and reaches the Stoney Trail ring road. Crisscrossing twice more with the river, it intersects Glenmore Trail and Memorial Drive; the former is a major east–west expressway while the latter is a freeway spur into downtown. In north Calgary, it crosses Highway 1 and passes Calgary International Airport before ending at a second interchange with Stoney Trail. Highway 2 becomes the Queen Elizabeth II Highway as it continues north into Rocky View County towards Red Deer and Edmonton.

Originally called Blackfoot Trail Freeway upon the opening of the first section in 1971, it was renamed in 1974 to honour Deerfoot, a late-19th-century Siksika Nation (Blackfoot) long-distance runner known for his exceptional speed. Subsequent sections opened in 1975, 1980, 1982 and 2003. Deerfoot was not entirely a freeway until 2005 when the final of four at-grade intersections in southeast Calgary was converted to an interchange. Well known for its frequent rush hour congestion and collisions, traffic levels have steadily increased as Calgary's population has tripled to over 1.3 million since 1971. The mostly six-lane freeway is Alberta's busiest road with volume reaching nearly 160,000 vehicles per day at Memorial Drive in 2022, twice that for which it was designed. The province of Alberta has been fiscally responsible for the road since 2000 but now seeks to offload maintenance and future improvement costs to the city of Calgary. The two parties remain at odds over who should operate the road in the long-term but completed a joint study in 2021 that offered long and short-term recommendations. In 2023, Aecon began a $615 million project which will add lanes in both directions, twin the Ivor Strong Bridge, and reconfigure various interchanges. All work is planned to be complete by 2027.

As a segment of Highway 2, Deerfoot Trail is a core route of the National Highway System and a key international corridor. It is also part of Calgary's Primary Goods Movement Network and is identified as a skeletal road in the city's Transportation Plan, a limited-access route important for long distance travellers, and is the only route that stretches the entire length of the city from north to south. From its split with Highway 2A (Macleod Trail) near the hamlet of De Winton in the south, it runs north to Stoney Trail at Calgary's northern city limit where it becomes the Queen Elizabeth II Highway. The freeway roughly bisects the city, though it lies entirely east of Centre Street which officially marks the boundary between the east and west side of the city. From its southern terminus until Memorial Drive, Deerfoot approximates the course of the Bow River. Initially the freeway is on the east side, then crosses to the west bank, and finally back to the east before the river and Memorial Drive veer west at Inglewood towards downtown. Most of the road's northern half parallels Nose Creek, a tributary of the Bow.

Deerfoot is a divided freeway for its entire 46.4-kilometre length, ranging from four to eight lanes wide. The northbound and southbound lanes are separated by an approximately 15-metre (49 ft) wide depressed grass median near De Winton, which narrows and becomes a combination of Jersey and constant-slope barriers through most of south Calgary before returning to grass of varying widths from 17 Avenue SE to the north terminus. In north Calgary the grass median is supplemented by 10.75 km (6.7 mi) of high-tension cable barriers (HTCB) that were added in 2007, virtually eliminating the risk of serious median collisions. It was the first major HTCB installation in Canada. The freeway has a posted speed limit of 110 km/h (68 mph) from its origin at Highway 2A until just after the first Bow River crossing, after which the limit is reduced to 100 km/h (62 mph) for the next 34 km (21 mi) through most of Calgary until Beddington Trail in the northeast where the limit returns to 110 km/h. The entire route is paved with asphalt, except for a 12 km (7.5 mi) concrete section in south Calgary.

Alberta Transportation, the branch of the Alberta government who operate and maintain all highways in the province, signed a contract with Carmacks Enterprises for maintenance of Deerfoot Trail from Stoney Trail in south Calgary to the northern city limit. The province intends to return control of the freeway to the city, but it is desirable for the city to avoid the significant maintenance and rehabilitation costs associated with the freeway and have the road remain under provincial control for as long as possible. Former Calgary mayor Rod Sykes said, "I wouldn’t take on the problems of the Deerfoot if I were at City Hall now."

Deerfoot Trail begins as a rural freeway near De Winton where two lanes fork to the northeast from Macleod Trail and descend across Dunbow Road toward the Bow River. It crosses the river on twin 236-metre (774 ft) bridges constructed over an environmentally sensitive area of the valley. Rising from the river, the freeway enters Calgary limits and its southern suburban neighbourhoods of Cranston and Seton to which access is provided by a partial cloverleaf interchange. A major junction at the Stoney Trail ring road immediately follows, with signage recommending that traffic destined for the International Airport, Edmonton, and Medicine Hat use eastbound Stoney Trail as a bypass. Continuing north as an eight lane freeway, Deerfoot passes between the communities of McKenzie Lake and McKenzie Towne, crossing 130 Avenue SE to the south terminus of Barlow Trail. It then reduces to six lanes, curving to the west through the neighbourhoods of Douglasdale and Douglasglen across the Bow River on the Ivor Strong Bridge, named after John Ivor Strong who served as Chief Commissioner for Calgary until 1971.

Immediately after the river, Deerfoot merges with the major routes of Anderson Road and Bow Bottom Trail, often a point of congestion at rush hour. In both directions, traffic through the outdated interchange is reduced from three lanes to two. The freeway curves north along the river's west bank to cross Southland Drive, paralleling Blackfoot Trail near the community of Acadia. North of Acadia, the freeway bisects a large area of commercial development for several kilometres before reaching a major interchange at Glenmore Trail. The interchange is generally identified as the second of two major congestion points on Deerfoot in south Calgary, the so called "Glenmore squeeze", where traffic is reduced to two lanes each way over Glenmore. Deerfoot turns sharply to the east and again crosses the Bow River on the Calf Robe Bridge, named after a Siksika Nation elder. Veering back to the north, it follows the river's east bank across Peigan Trail to a partial cloverleaf interchange at 17 Avenue SE, passing the neighbourhoods of Dover and Southview. Deerfoot meets Memorial Drive, a major freeway spur into downtown, near Pearce Estate Wetland, Wilder Institute/Calgary Zoo and the Max Bell Centre, and continues into north Calgary while the Bow River turns west towards downtown.

In north Calgary, the freeway climbs along the east side of Nose Creek, a tributary of the Bow River. From Memorial Drive, it passes the Vista Heights neighbourhood to 16 Avenue NE (Highway 1/Trans-Canada Highway); this section has been largely unchanged since its completion in 1975. The six lane freeway enters light commercial development north of 32 Avenue NE and passes McKnight Boulevard, providing access to airport-related light industrial areas as well as Nose Hill Park, which is visible to the west.. Access to Huntington Hills and Deerfoot Mall are then provided by an interchange at 64 Avenue NE. Beddington Trail splits to the northwest from Deerfoot, following Nose Creek into a large residential area of north Calgary that includes the neighbourhoods of Country Hills, Panorama Hills, and Hidden Valley. The speed limit on Deerfoot increases to 110 km/h as development tapers in an increasingly rural area of north Calgary. After West Nose Creek Park, an interchange with Airport Trail serves as the primary access for Calgary International Airport, and to the west, the neighbourhood of Harvest Hills via 96 Avenue NE. North of Airport Trail, the freeway curves northeast through light commercial areas across Country Hills Boulevard and ends at an interchange with Stoney Trail. It continues north to Airdrie as the Queen Elizabeth II Highway.