501 Queen is an east–west Toronto streetcar route in Ontario, Canada, operated by the Toronto Transit Commission (TTC). It stretches from Neville Park Loop in the east, running along Queen Street and in a reserved right-of-way within the median of the Queensway to Humber Loop in the west. In the late evenings, the 501 Queen route is extended west from Humber Loop, running on Lake Shore Boulevard to Long Branch Loop, replacing route 507 Long Branch. This route operates as part of the TTC's Blue Night Network service, operating in the early morning hours as the 301 Queen.

The Toronto streetcar system is a network of eleven streetcar routes in Toronto, Ontario, Canada, operated by the Toronto Transit Commission (TTC). It is the third busiest light-rail system in North America. The network is concentrated primarily in Downtown Toronto and in proximity to the city's waterfront. Much of the streetcar route network dates from the 19th century. Three streetcar routes operate in their own right-of-way, one in a partial right-of-way, and six operate on street trackage shared with vehicular traffic with streetcars stopping on demand at frequent stops like buses. Since 2019, the network has used low-floor streetcars, making it fully accessible.