Line 5 Eglinton is a light rail line that is under construction in Toronto, Ontario, Canada. Owned by Metrolinx and operated by the Toronto Transit Commission (TTC), the line will be part of the Toronto subway system as its fifth route. The first phase of the 19-kilometre (12 mi) line will include 25 stops along Eglinton Avenue, from Mount Dennis station mostly underground to Laird station, after which it will run predominantly at-grade within the street's median to Kennedy station, where it will connect underground with Line 2 Bloor–Danforth. The second phase, a 9.2-kilometre (5.7 mi) westward extension from Mount Dennis, will run mostly underground or elevated to Renforth station, with seven new stations.

Metrolinx is a Crown agency of the Government of Ontario that manages and integrates road and public transport in the Greater Toronto and Hamilton Area (GTHA), which comprises much of Ontario's Golden Horseshoe region. Headquartered at Union Station in Toronto, the agency was created as the Greater Toronto Transportation Authority on June 22, 2006. The agency adopted its present name as a brand name in 2007 and eventually as the legal name in 2009.