While the market has focused this week on the woes of Chesapeake Energy, which denied on Monday it was considering bankruptcy, this is not the only energy company where Mr Icahn is nursing a paper loss of $1.1bn.
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Shares in Cheniere Energy, which ousted its founder and chief executive Charif Souki in December, are now languishing almost 60 per cent below Mr Icahn's average purchase price, giving him a similar sized paper loss to Chesapeake.
He originally invested $1.3bn in Chesapeake, and $1.9bn in Cheniere.
Icahn Enterprises, which is itself 90 per cent owned by Mr Icahn, has lost almost a quarter of its value this year and is down 68 per cent since its post-crisis peak in 2013. The company's shares were trading at $46.87 on Tuesday afternoon in New York.
As well as its exposure to Mr Icahn's equity investments, the company serves as a holding entity for subsidiaries spanning railcar manufacturing, casinos and car parts.
Icahn Enterprises is scheduled to report its 2015 results this month, giving details of Mr Icahn's equity investment performance for the year as a whole.
Those investments were down 2.8 per cent in the first nine months of 2015, compounding the woes of the previous year, when the declining oil price first began to weigh on his energy holdings. He was down 6.4 per cent in 2014, his first negative year since 2008.
The only energy company in which Mr Icahn holds a significant stake and where he is up on the deal is CVR Energy, which focuses on oil refining.
The data are based on calculations of Mr Icahn's average purchase price made by Bloomberg and on the most recent regulatory filings by him and the web of investment vehicles he uses to buy shares.
The misfiring investments in oil and gas have made a significant dent in Mr Icahn's personal wealth, which was estimated in March last year by Forbes magazine at $23.5bn.
Mr Icahn did not respond to a request to comment. He had expanded his investments in the oil and gas sector throughout 2015, adding the Freeport-McMoran stake and increasing the holdings at Cheniere.
At a conference in December, Mr Icahn said the scale of the oil price slide had taken everyone by surprise, adding he thought it could go lower before rebounding.
Chesapeake shares lost one-third of their remaining value on Monday following a report that it had hired restructuring lawyers. The company said it was using Kirkland and Ellis, its advisers since 2010, "to advise the company as it seeks to further strengthen its balance sheet", but that it was not planning to go bankrupt.