Vernon Unsworth claims the billionaire defamed him with “unlawful, unsupportable and reprehensible accusations”, court documents seen by Sky News say.
They also say that Mr Musk “falsely conveyed that [the] United Kingdom citizen…is a paedophile and child rapist”.
Mr Unsworth was part of the team of international divers who became known worldwide after they successfully rescued all 12 youngsters and their football coach when they became trapped by rising waters in a Thai cave complex.
From 15 July to 30 August, 2018, Mr Musk used his Twitter account and emails to the media to “publish to the world false and defamatory accusations against Mr Unsworth,” the documents said.
Mr Unsworth holds Mr Musk “legally accountable for his wrongdoing and to vindicate his reputation,” they add.