The company was established in 2000 by the merger of Glaxo Wellcome (formed from the acquisition of Wellcome plc by Glaxo plc) and SmithKline Beecham plc (formed from the merger of Beecham plc and SmithKline Beckman Corporation, which in turn was formed by combining the Smith Kline French and Beckman companies). In 2022, the company changed its name to GSK plc, formerly being known as GlaxoSmithKline plc.

The company has a primary listing on the London Stock Exchange (LSE) and is a constituent of the FTSE 100 Index. As of October 2022 it had a market capitalisation of $61 billion, the eigth-largest of any company listed on the LSE. It has a secondary listing on the New York Stock Exchange. Emma Walmsley has been the chief executive officer since April 2017.

As of 2021, the UK-based pharma giant ranked ninth-largest in the world in terms of revenue.

GSK manufactures drugs and vaccines for major disease areas such as asthma, cancer, infections, diabetes, digestive and mental health conditions. Many medicines were historically discovered or developed at GSK and its predecessor companies and are now sold as generics.