Tesco plc () is a British multinational groceries and general merchandise retailer headquartered in Welwyn Garden City, England. In 2011 it was the third-largest retailer in the world measured by gross revenues and the ninth-largest in the world measured by revenues. It has shops in Ireland, the United Kingdom, the Czech Republic, Hungary, and Slovakia. It is the market leader of groceries in the UK (where it has a market share of around 28.4%).

Tesco has expanded globally since the early 1990s, with operations in 11 other countries in the world. The company pulled out of the US in 2013, but as of 2018 continues to see growth elsewhere. Since the 1960s, Tesco has diversified into areas such as the retailing of books, clothing, electronics, furniture, toys, petrol, software, financial services, telecoms and internet services. In the 1990s, Tesco re-positioned itself from being a downmarket high-volume low-cost retailer, attempting to attract a range of social groups with its low-cost "Tesco Value" range (launched 1993) and premium "Tesco Finest" range.

Tesco is listed on the London Stock Exchange and is a constituent of the FTSE 100 Index.