Soon after Icahn was named as Trump's special adviser on regulatory reform in December, Democratic critics decried what that his unofficial role was a conflict of interest because he continued to run his businesses.
But Icahn - who made his name and fortune as a corporate raider - indicated that his resignation was due to criticism regarding the appearance of possible ethical conflicts.
The activist investor, who leads Icahn Enterprises LP, was an early and close ally of Trump who was often praised by the Republican for his business acumen.
Icahn is the latest in a series of people to quit as Trump advisers or officials.
Icahn's departure followed a flurry of changes at the White House. Trump on Friday fired his chief strategist Stephen Bannon, two days after disbanding two high-profile business advisory groups.
The post linked to a letter on his website, in which he stated that he "never had a formal position" with the Trump administration. "Indeed, out of an abundance of caution, the only issues I ever discussed with you were broad matters of policy".
However, Icahn did not cite Charlottesville in his decision to step away from his advisory role, insisting in his statement that he had "no duties whatsoever" and choosing to move on to avoid "partisan bickering" about his role.
Yet Icahn had strong views on a regulation that was hurting his company, CVR Energy.
On the campaign trail, Trump praised Icahn as the kind of tenacious deal-maker that he would bring into his administration.
Icahn's involvement with Trump has frequently come under criticism from Democrats who, in May, asked US regulators to investigate Icahn's activities in the USA biofuels blending credit market. "He is advising the Trump Administration on issues involving regulatory overhaul, helping to select the heads of key regulatory agencies like the Securities & Exchange Commission and the Environmental Protection Agency".
The senators claimed Icahn significantly benefited from a policy proposal to shift the burden of complying with biofuel quotas from refiners to fuel blenders.
"I sincerely regret that because of your extremely busy schedule, as well as my own, I have not had the opportunity to spend almost as much time as I'd hoped on regulatory issues", Icahn wrote.