Those on trial include the owners of the Mossack-Fonseca law firm that was at the heart of the 2016 massive document leak.
The Panama Papers include a collection of 11 million secret financial documents that illustrate how some of the world's richest people hide their money.
The repercussions of the leaks have been far-ranging, prompting the resignation of the prime minister of Iceland and bringing scrutiny to the leaders of Argentina and Ukraine, Chinese politicians and Russian President Vladimir Putin, among others.
The often-delayed trial opened with lawyers Juergen Mossack, Ramon Fonseca and other former representatives, lawyers or ex-employees of the firm facing money laundering charges.
Mossack was present in the courtroom, and said: "I am not guilty of such acts."
Lawyers for Fonseca said he was in a hospital in Panama.
The case centres on allegations the firm set up shell companies to acquire properties in Panama with money from a sprawling corruption scheme in Brazil known as the Car Wash, or Lava Jato in Portuguese.
Fonseca has said the firm, which closed in 2018, had no control over how its clients might use offshore vehicles created for them. Both Mossack and Fonseca have Panamanian citizenship, and Panama does not extradite its own citizens.
The two were acquitted on other charges in 2022.
The records were first leaked to the German daily Suddeutsche Zeitung, and were shared with the International Consortium of Investigative Journalists, which began publishing collaborative reports with news organisations in 2016.
US prosecutors have alleged Mossack Fonseca conspired to circumvent American laws to maintain the wealth of its clients and conceal tax dollars owed to the IRS. They alleged the scheme dates to 2000 and involved sham foundations and shell companies in Panama, Hong Kong and the British Virgin Islands.
15°C