Nortel Networks Corporation (Nortel), formerly commonly known as Northern Electric and Northern Telecom, was a multinational telecommunications and data networking equipment manufacturer headquartered in Mississauga, Ontario, Canada. It was founded in Montreal, Quebec, in 1895 as the Northern Electric and Manufacturing Company. Until an antitrust settlement in 1949, Northern Electric was owned principally by Bell Canada and the Western Electric Company of the Bell System, producing large volumes of telecommunication equipment based on licensed Western Electric designs.

At its height, Nortel accounted for more than a third of the total valuation of all the companies listed on the Toronto Stock Exchange (TSX), employing 94,500 people worldwide.

In 2009, Nortel filed for bankruptcy protection in Canada and the United States, triggering a 79% decline of its corporate stock. The bankruptcy case was the largest in Canadian history, and left pensioners, shareholders and former employees with enormous losses. By 2016 Nortel had sold billions of dollars' worth of assets. Courts in the U.S. and Canada approved a negotiated settlement of bankruptcy proceedings in 2017.