GlaxoSmithKline plc (LSE: GSK NYSE: GSK), often abbreviated to GSK, is a global pharmaceutical, biologics, vaccines and consumer healthcare company headquartered in London, United Kingdom. It is the world's third largest pharmaceutical company measured by revenues (after Johnson & Johnson and Pfizer). It has a portfolio of products for major disease areas including asthma, cancer, virus control, infections, mental health, diabetes and digestive conditions. It also has a large consumer healthcare division which produces and markets oral healthcare products, nutritional drinks and over-the-counter medicines, including Sensodyne, Horlicks and Gaviscon.
Its primary listing is on the London Stock Exchange and it is a constituent of the FTSE 100 Index. It has a secondary listing on the New York Stock Exchange.
GSK was formed in 2000 by the merger of GlaxoWellcome plc (formed from the acquisition of Wellcome plc by Glaxo plc), and SmithKline Beecham plc (from the merger of Beecham plc, and SmithKlineBeckman Corporation).