Mossack Fonseca & Co. was a Panamanian law firm and corporate service provider. At one time it was the world's fourth-largest provider of offshore financial services. From its establishment in 1977 until the publication of the Panama Papers in April 2016, the company remained mostly obscured from public attention, even though it was a major firm in the global offshore industry and acted for approximately 300,000 companies. Prior to its dissolution, the company employed roughly 600 staff members spread across 42 countries.

The Panama Papers are 11.5 million leaked documents that were published beginning on April 3, 2016. The papers detail financial and attorney–client information for more than 214,488 offshore entities. The documents, some dating back to the 1970s, were created by, and taken from, former Panamanian offshore law firm and corporate service provider Mossack Fonseca, and compiled with similar leaks into a searchable database.