Endo International plc is an American Irish-domiciled generics and specialty branded pharmaceutical company that generated over 93% of its 2017 sales from the U.S. healthcare system. While Endo's management, operations, and customers are almost exclusively U.S.–based, in 2013 Endo executed a corporate tax inversion to Ireland to avoid U.S. corporate taxes on their U.S. drug sales, and to avail of Ireland's corporate tax system.

In 1920, Intravenous Products of America was incorporated as a privately owned pharmaceutical business operating in New York. By 1935 it had changed its name to Endo Products. The product line focused on medication for the treatment of pain (e.g. Percodan), a focus which continued during its acquisition by DuPont in 1969 (e.g. Percocet).

Endo Pharmaceuticals Holdings was created as a result of a $277 million management buyout of the division from DuPont Merck in 1997, led by Carol Ammon. Through the merger with Algos, it changed name again to Endo Pharmaceuticals Holdings Inc. and began trading as a public company.

In 2012 shareholders voted to again change name to Endo Health Solutions, with Endo Pharmaceuticals becoming a segment of the business. Through the 2014 acquisition of Paladin Labs and subsequent corporate restructuring, Endo International plc was formed.

In 2022, Endo's stock fell below $1 as the company faced restructuring of its $8 billion of debt.

On August 17, 2022 Endo International Plc filed for Chapter 11 bankruptcy protection after reaching a $6 billion deal with some of its creditors that related to opioid litigation in the US and a $6 billion deal with creditors, including for settling lawsuits.

The United States Department of Justice has objected to the plans, claiming they violate bankruptcy law.

In March 2025, Mallinckrodt and Endo announced plans to merge in a deal valued at $6.7 billion.