Edmonton Light Rail Transit, commonly referred to as the LRT, is a light rail system in Edmonton, Alberta. Part of the Edmonton Transit Service (ETS), the system has 29 stations on three lines and 37.4 km (23.2 mi) of track. Much of the system has a dedicated right-of-way, while in the downtown area, vehicles run underground. As of 2018, it was the seventh busiest light rail transit system in North America, with over 113,000 daily weekday riders.

The ETS started operation of the original LRT line in 1978, expanded by 2010 into the Capital Line, running between Clareview in Edmonton's northeast and Century Park in Edmonton's south end. The first phase of the newer Metro Line started service between the University of Alberta campus and hospital in Edmonton's south-central and the Northern Alberta Institute of Technology northwest of downtown Edmonton in 2015, with further expansion to north Edmonton and neighbouring city of St. Albert planned into the future. Construction of the first phase of the 27-kilometre (17 mi) Valley Line, from downtown Edmonton to Mill Woods in southeast Edmonton, began in spring 2016, and opened November 4, 2023. Construction on the second phase of the Valley Line, connecting downtown to west Edmonton, began in fall 2021 and is scheduled for completion by 2028.

Edmonton's population grew rapidly in the decades after the Second World War, going from 160,000 residents in 1951 to 451,000 in 1976. During the 1960s and early 1970s, city-commissioned studies recommended a number of city-wide transportation systems such as heavy rail transit lines, and freeway networks. The city opted to study LRT as a "balanced" solution; being more cost effective and flexible than heavy rail (i.e., subways), but higher-capacity and less expensive in the long-term than bus-only networks utilizing freeways.

Edmonton's northeast section was selected as the first area to receive transportation improvements, because its road network was at risk of being overwhelmed by new developments. City Council was presented with three options in 1974: 1) A freeway-bus option, which would require 70 buses in peak hours, require substantial land acquisition, and reduce potential transit ridership; 2) an all-bus option that would require 150 buses in peak hours, which would share traffic lanes with vehicles aside from limited bus-priority measures, and; 3) an integrated option that required 75 buses in peak hours, and 14 LRT cars on a northeast line. The third option had the lowest ongoing costs of the three, and City Council approved it in 1973 despite provincial funding not being secured yet. In 1974, the Alberta Government pledged $45 million over four years, which was the original estimated cost of construction.

Construction began in 1974 with a budget of $65 million. During planning and construction, the managers of various departments and city-owned utilities coordinated through a Municipal Planning Commission, which allowed the city to reserve a path for the LRT; this included controlling the location of piles under the Edmonton Plaza Hotel to allow for LRT tunnels to be constructed later. As well, members of the University of Alberta's Faculty of Engineering served as advisors for the project, and conducted research in areas such as transportation planning, traffic management, soil mechanics, and tunnelling.

Edmonton became the first city in North America with a metropolitan population of less than one million to build a modern light rail system. It also became the first city in Western Canada to operate a rapid transit system. Testing of the new line started in 1977 with regular service starting April 22, 1978, in time for the 1978 Commonwealth Games. The line followed a CN right-of-way from Belvedere Station to Stadium Station (near Commonwealth Stadium), via an intermediate stop at Coliseum Station (near Northlands Coliseum), and then continued in a tunnel under 99 Street to Central Station, at Jasper Avenue and 100 Street, including an intermediate stop at Churchill Station. The original line was 6.9 km (4.3 mi) long.

Planning influences included the rail systems of Toronto (for dimensions), Montreal (underground environment), Cleveland (reuse of existing rail right of way), as well as Netherlands and Germany (feeder bus routes with timed-transfers, and choice of rolling stock). Operating practices were influenced by the MBTA Green Line, British trams, and the Canadian National Railway.

When the line opened, fare collection was modelled on traditional rapid transit lines, with booth attendants. Low volumes of activity at some entrances led to weekend closures of alternate station entrances. In November 1980, Edmonton Transit (as it was then named) switched to a modified European-style "proof of payment" system, retaining the old turnstiles to issue the new receipts. Fares were now collected by automated ticket vending machines with irregular proof of payment inspectors, which permitted keeping all entrances open and required fewer staff.