Icahn developed a reputation as a ruthless "corporate raider" after his hostile takeover of TWA in 1985. The result of that takeover was Icahn systematically selling TWA's assets to repay the debt he used to purchase the company, which was described as asset stripping. In 1988, Icahn took TWA private, gaining a personal profit of $469 million, and leaving TWA with a debt of $540 million. In 1991, Icahn sold TWA's prized London routes to American Airlines for $445 million.
Icahn also attempted the grand prize of U.S. Steel, launching a hostile takeover for 89% of the industrial giant for $7 billion ($14.9 billion in 2012) in late 1986. He was finally rebuffed by CEO David Roderick on January 8, 1987.
In 2004, Icahn purchased a large block of stock of Mylan Laboratories. After Mylan had announced a deal to acquire King Pharmaceuticals. Icahn threatened a proxy fight over the acquisition, on the ground that the deal required Mylan to overpay. In early 2005, Mylan gave up its efforts to acquire King, but according to the management, the decision was made after it monitored relevant facts, not due to pressure from Icahn.
In 2006, Icahn sold his stake in KT&G (Korea Tobacco & Ginseng) for a substantial profit.
Icahn made an attempted run as a major shareholder of Time Warner, owning about 3.3% of the company valued at billions of dollars. He has been actively seeking to influence the direction of Time Warner, often in conflict with its former chief executive, Richard Parsons. Although Time Warner recently sold 5% of its AOL division, Icahn has been pressing for additional action to increase shareholder value. On February 7, 2006, a group led by Icahn and Lazard Frères CEO Bruce Wasserstein unveiled a 343-page proposal calling for the breakup of Time Warner into four companies and stock buybacks totaling approximately $20 billion. On February 17, 2006, the Icahn-led group agreed with Time Warner to not contest the re-election of Time Warner's slate of board members at the 2006 shareholders meeting. In exchange for the Icahn group's cooperation, Time Warner would buy back up $20 billion of stock, nominate more independent members to the board of directors, cut $1 billion of costs by 2007, and continue discussions with the Icahn group over their proposal, particularly on the future of Time Warner Cable.
In 2008, Icahn showed interest in the takeover of Yahoo! and the ousting of Jerry Yang from his position as CEO to allow Microsoft to purchase the web company.
Icahn's hedge funds currently own 5.6% of biotechnology company Biogen Idec. Beginning in 2007, Icahn has steadily increased his stake in Biogen, seeking to possibly acquire, break up, and/or sell off various parts of the company. As of June 2009, Icahn has managed to seat two of his allies on Biogen's board with the apparent goal of splitting the company into two entities and possibly replacing CEO James C. Mullen, of whom he has been highly critical.[dated info]
In July 2010, Icahn acquired a 14 percent stake in Mentor Graphics. Based on this acquisition, Mentor Graphics signed a Poison Pill provision. As of September 2010, Icahn owns just less than 15 percent of Mentor Graphics. On February 22, 2011 he made an offer to buy Mentor Graphics for about $1.86 billion in cash in a move to push other suitors to declare themselves. On October 31, 2012 Icahn bought 5.5 million shares of the internet video service provider Netflix taking a 10% stake in the company.
In February 2013 Forbes listed Icahn as one of the 40 Highest-Earning hedge fund managers.
In July 2013 Icahn started an attempt to acquire Dell Inc.
On August 13, 2013 Icahn announced that his new stock pick is Apple, pushing the stock 5% up which breaks its 200-day moving average for the first time in the year.
In October 2013, Icahn acquired around 61 million shares in Talisman Energy prompting shares in the ailing Canadian oil producer to surge. He also announced he would seek a seat on the board of the company.
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XO Holding in 2005 announced to sell the wired part of its business for $700 million to its majority shareholder and chairman Icahn himself to pay back its debts and buy back its preferred stock for about $600 million – all owned by Icahn himself. He would end up owning XO's traditional wired phone business outright, and still own his 60 percent stake in what would be left of XO. In the SEC filings, XO explained that a special committee of its board of directors weighed Icahn's bid and declared it to be in the best interest of shareholders. Investment bankers determined Icahn's offer to be "fair". And the stockholders would approve the transaction because Icahn owned 60% of the common stock and the directors, named by Icahn, hired the investment bankers to put their stamp of approval on his offer. However, R2 and other minority shareholders successfully defeated the attempt and the Delaware Court on March 31, 2008, entered a final judgment order: 1. Reduced by 1.5% of the interest on the debt held by Icahn; 2. Waived, through the due date of July 15, 2009 for any breach of the financial covenants with the Chairman; 3. Awarded $8 million to R2's and other minority shareholders’ attorneys at Icahn's cost and other damages to the business caused by Icahn's self-dealing and/or conflict of interest.
In August 2006, he bought stock in the video game publisher Take-Two Interactive. He increased his stake to 11.3% on December 21, 2009, making him the company's second largest shareholder.
In January 2007, he purchased a 9.2% stake in Telik (Nasdaq: TELK), a biotech company engaged in cancer research, because he believed its shares were undervalued.
On January 16, 2007, it was disclosed in a Securities and Exchange Commission filing that Icahn is the beneficial owner of 14.57%, or 6.1 million shares, of WCI Communities (NYSE: WCI). In the filing Icahn indicated that he intends to contact WCI to discuss how to "unlock the inherent value" of its shares.
On January 30, 2007, Motorola (then NYSE:MOT, now two separate entities: Motorola Mobility(NYSE: MMI) and Motorola Solutions (NYSE: MSI)) said it received notice that Icahn owns about 33.5 million shares, representing a 1.39% interest in the company and pressed for a seat on its board. But he was turned down by the majority of the stockholders in the election for Board of Directors which was held on May 8.
On February 9, 2007, Lear Corporation's (NYSE: LEA) board of directors agreed to a $2.3 billion takeover offer from Icahn, pending a 45-day solicitation period for other offers, which it did not receive, and shareholder approval.
On February 27, 2007, Icahn invested $50 million in Motricity, a North Carolina-based provider of mobile content delivery technology.
During April 2007, Icahn successfully pressured Medimmune (MEDI) to consider takeover bids. The company was bought out by AstraZeneca.
On May 7, 2007, Icahn's quest for a board seat on Motorola was effectively ended, as the company announced the next day that in a preliminary count of the votes for board members Icahn did not have enough to be elected. Icahn stated that he would not sell his shares in the company.
On September 14, 2007, Icahn disclosed his ownership of 8.5% of outstanding shares in business software company BEA Systems. BEA Systems shares rose more than 4% after Icahn disclosed his stake in a filing with the Securities and Exchange Commission. In the filing, Icahn, known for forcefully pushing an agenda at companies where he acquires ownership, suggested that BEA Systems should put itself up for sale. By September 21, Icahn increased his stake to 9.88% of BEA, and on October 3, to 11.05%, and then to 13.22% on October 4, 2007. On January 16, 2008, Oracle Corporation announced it was purchasing BEA Systems.
On February 21, 2008, Icahn sold his American Casino & Entertainment Properties, which owned four casinos in Southern Nevada (three in Las Vegas, and one in Laughlin). The announcement had been made on April 23, 2007. The purchaser was an affiliate of Goldman Sachs and the price was $1.3 billion.
On March 21, 2008, Icahn appeared on Nightly Business Report and discussed his views on proxy fights.
On March 24, 2008, Icahn sued Motorola as part of his effort to gain four seats on Motorola's board and force a sale of its mobile business.
On May 13, 2008, Icahn purchased as many as 50 million shares of Yahoo, leaning toward launching a proxy contest.
On May 15, 2008, Icahn confirmed that he would be commencing a proxy fight to remove Yahoo's board of directors in response to their "irrational" actions in rejecting Microsoft's takeover bid.
On June 18, 2008, Icahn launched The Icahn Report.
On July 21, 2008, Icahn agreed to join Yahoo's board of directors in a deal that would end the proxy fight. The agreement called for the Yahoo board to expand by two directors to eleven members. Eight directors would stand for re-election while the remaining three seats would include Icahn and two nominees that Icahn recommended.
In September/October 2008 Icahn was involved in the attempted purchase of Imclone by Bristol Myers Squibb (which was turned down) and eventual sale of Imclone to Eli Lilly in an all cash deal valued at $6.5 billion. Icahn had described Bristol Myers Squibb's upwardly revised offer of $62 per share as "absurd".
In December 2008, Icahn filed suit against Realogy over a proposed debt swap.
On April 20, 2009, Carl Icahn's proxy battle for Amylin was thought to be an attempt to engineer a sale to Lilly.
On September 28, 2009, XO Holdings (XOHO) rejected Icahn's offer to buy out the remaining shares of XO he did not own already for 55 cents a share, saying the offer "substantially undervalues" the company. Icahn previously attempted to buy the telecom assets from XO but dropped the bid because of shareholders opposition. A lawsuit filed by the hedge fund and minority shareholder R2 in August 2009 alleged Icahn as director and majority owner of XO hurt shareholders by refusing refinance of the debts owned by Icahn when capital was easily available and repeatedly denying acquiring attempts at prices several times higher than Icahn's offer. On October 26, 2009 Icahn raised his offer to 80 cents a share. The offer expired on the same day a filing disclosed its existence.
On October 23, 2009, Icahn announced his resignation from the board of directors at Yahoo!
On February 16, 2010, it was revealed that Icahn had reduced his equity stake in Yahoo! from a one-time high of 75 million shares to 12 million shares.
On February 18, 2010, Icahn, through a subsidiary of his Icahn Enterprises LP, acquired from Fontainebleau Las Vegas, LLC and certain affiliated entities the Fontainebleau property and improvements thereon located in Las Vegas, Nevada, for an aggregate purchase price of approximately $150 million. Icahn expressed confidence in the acquisition of the 70% complete Fontainebleau property stating that "The acquisition of the Fontainebleau property was a great opportunity to purchase a distressed asset that I believe has considerable value." 
On May 17, 2010, Icahn reported that he owns almost 12% of Hain Celestial Group Inc. (HAIN).
On May 25, 2010, Icahn reported that he bought an 8.54% stake in Lawson Software as of May 11. (LWSN).
On May 27, 2010, Icahn reported that he had accumulated a 6.9% stake in Mentor Graphics. (MENT). On March 15, 2011, Mentor's board issued a strong warning to its shareholders against a proxy action by Icahn.
On February 11, 2011, Icahn reported that he had accumulated a 9.08% stake in The Clorox Company (CLX). Shares jumped over 9% that day on the news.
In January 2011, he again proposed to purchase all the XO Holder common stock he did not already own for $0.70 per share. The board hired JP Morgan for evaluation. On July 12, 2011, Icahn and his affiliates raised the price to $1.40. In addition to R2's suit, five class actions complained that the offer was inadequate and that Icahn's self-dealing had illegally depressed the stock price in order to take the company private cheaply and use the $3.5 billion NOLs by himself.
On July 15, 2011, Icahn offered to purchase The Clorox Company for $76.50 a share in a deal worth $12.6 billion. He then stated that if the deal falls through, he will pay Clorox $100 million.
On September 27, 2011, Icahn was rumored to have purchased a stake in Canadian telecom company Research in Motion, sending their share price up by as much as 7%. On October 17, 2011, Icahn denied the rumour.
On October 31, 2012, Icahn purchased a 10% stake in Netflix.
On November 26, 2012, Ichan revived his proxy battle over control of the Oshkosh Corp. board of directors, more than doubling up on his previous effort by nominating a slate of 13 directors, including himself.
On April 2, 2013, Icahn disclosed that he owned a 9.2% stake in Nuance Communications, Inc. [NUAN], pushing entrenched management to "divest and restructure" its 1.4 billion dollar [net] debt and sell off non-performing asserts.
On August 2, 2013, Icahn sued computer giant Dell and its board in an attempt to derail a $24.4 billion buyout bid by the CEO, Michael Dell, in favor of his own rumored forthcoming bid.
On August 13, 2013, Icahn "tweets" about his large stake in Apple Inc. (AAPL). He claims that the company is extremely undervalued and adds that he urges CEO Tim Cook for a larger share buyback.  As a result, AAPL shares surged 5% by the end of close on this day, and an additional 1.82% on August 14 2013. This allowed AAPL stock to cross a key psychological resistance of $500. 
In October of 2013 Ichan sold about 4% of his shares in Netflix for a profit in excess of 800 million in less than one year. This is believed to be one of the largest stock gains in history.
Icahn has been married twice.
In 1979, he married Liba Trejbal, a Czech ballerina from the former Czechoslovakia. They separated in 1993 and divorced in 1999 after years of litigation. Liba had sought to invalidate a prenuptial agreement she had signed prior to their marriage claiming duress as she was pregnant at the time. Liba originally fought Icahn's offer of roughly $1.5 million a year because he was worth billions at the time and eventually settled for an undisclosed amount. They have two children, Brett (b. 1979) and Michelle (b. 1982).
In 1999, he married his longtime assistant and former broker, Gail Golden. She has two children, Shana L. Golden and Christie R. Golden, from a prior marriage.
Icahn Stadium on Randall's Island in New York City is named after him, as is the Carl C. Icahn Center for Science and Icahn Scholar Program at Choate Rosemary Hall, a New England prep school. This organization pays for tuition, room and board, books, and supplies for 10 students every year for four years (freshman-senior), an expense that adds up to about $160,000 per student.
His foundation, the Children's Rescue Fund, built Icahn House in The Bronx, a 65-unit complex for homeless families consisting of single pregnant women and single women with children, and operates Icahn House East and Icahn House West, both of which are homeless shelters located in New York City.
Icahn has received numerous awards, including the Starlight Foundation's Founders Award and its 1990 Man of the Year Award. He was also named Guardian Angel 2001 Man of the Year. In 2004, he was honored by the Center for Educational Innovation - Public Education Association for his work with charter schools. In 2006, he was honored with the 100 Women in Hedge Funds Effecting Change Award for his outstanding contributions to improving education.
As of March 2013, his net worth is estimated to be $20 billion.
In 1985 Icahn established Foxfield Thoroughbreds, a horse breeding operation. At that year's Newstead Farm Trust sale run by Fasig-Tipton, he paid $4 million for Larida, a 6-year-old mare and a record $7 million for the 4-year-old bay mare Miss Oceana who was in foal to champion sire, Northern Dancer.