Thomson Reuters Corporation is a Canadian multinational mass media and information firm. The firm was founded in Toronto, Ontario, Canada, where it is headquartered at 333 Bay Street in Downtown Toronto. Thomson Reuters was created by the Thomson Corporation's purchase of British-based Reuters Group in April 2008, and is majority owned by The Woodbridge Company, a holding company for the Thomson family. Thomson Reuters was ranked as Canada's "leading corporate brand" in the 2010 Interbrand Best Canadian Brands ranking. Thomson Reuters operates in more than 100 countries, and has more than 45,000 employees.

The Thomson Corporation company was founded by Roy Thomson in 1934 in Ontario as the publisher of The Timmins Daily Press. In 1953, Thomson acquired the Scotsman newspaper and moved to Scotland the following year. He consolidated his media position in Scotland in 1957 when he won the franchise for Scottish Television. In 1959, he bought the Kemsley Group, a purchase that eventually gave him control of the Sunday Times. He separately acquired the Times in 1967. He moved into the airline business in 1965, when he acquired Britannia Airways and into oil and gas exploration in 1971 when he participated in a consortium to exploit reserves in the North Sea. In the 1970s, following the death of Lord Thomson, the company withdrew from national newspapers and broadcast media, selling the Times, the Sunday Times and Scottish Television and instead moved into publishing, buying Sweet & Maxwell in 1988. The company at this time was known as the International Thomson Organization Ltd.

In 1989, ITOL merged with Thomson Newspapers, forming The Thomson Corporation. In 1996, The Thomson Corporation acquired West Publishing, a purveyor of legal research and solutions including Westlaw.

Reuters Group the Company was founded by Paul Julius Reuter in 1851 in London as a business transmitting stock market quotations. Reuter set up his "Submarine Telegraph" office in October 1851 and negotiated a contract with the London Stock Exchange to provide stock prices from the continental exchanges in return for access to London prices, which he then supplied to stockbrokers in Paris, France. In 1865, Reuters in London was the first organization to report the assassination of Abraham Lincoln. The company was involved in developing the use of radio in 1923. It was acquired by the British National & Provincial Press in 1941 and first listed on the London Stock Exchange in 1984. Reuters began to grow rapidly in the 1980s, widening the range of its business products and expanding its global reporting network for media, financial and economic services: key product launches included Equities 2000 (1987), Dealing 2000-2 (1992), Business Briefing (1994), Reuters Television for the financial markets (1994), 3000 Series (1996) and the Reuters 3000 Xtra service (1999).

The Thomson Corporation acquired Reuters Group PLC to form Thomson Reuters on April 17, 2008. Thomson Reuters operated under a dual-listed company (“DLC”) structure and had two parent companies, both of which were publicly listed — Thomson Reuters Corporation and Thomson Reuters PLC. In 2009, it unified its dual listed company structure and stopped its listing on the London Stock Exchange and NASDAQ. It is now listed only as Thomson Reuters Corporation on the New York Stock Exchange and Toronto Stock Exchange (symbol: TRI).