Lehman Brothers Holdings Inc. (Pink Sheets: LEHMQ, former NYSE ticker symbol LEH) (pronounced /ˈleɪmən/) was a global financial-services firm that, until declaring bankruptcy in 2008, participated in business in investment banking, equity and fixed-income sales, research and trading, investment management, private equity, and private banking. It was a primary dealer in the U.S. Treasury securities market. Its primary subsidiaries included Lehman Brothers Inc., Neuberger Berman Inc., Aurora Loan Services, Inc., SIB Mortgage Corporation, Lehman Brothers Bank, FSB, Eagle Energy Partners, and the Crossroads Group. The firm's worldwide headquarters were in New York City, with regional headquarters in London and Tokyo, as well as offices located throughout the world.

On September 15, 2008, the firm filed for Chapter 11 bankruptcy protection following the massive exodus of most of its employees and clients, drastic losses in its stock, and devaluation of its assets by credit rating agencies. The filing marked the largest bankruptcy in U.S. history. The following day, the British bank Barclays announced its agreement to purchase, subject to regulatory approval, Lehman's North American investment-banking and trading divisions along with its New York headquarters building. On September 20, 2008, a revised version of that agreement was approved by Judge James Peck.

On September 22, 2008, Nomura Holdings announced that it had agreed to acquire Lehman Brothers' franchise in the Asia Pacific region, including Japan, Hong Kong and Australia. The following day, Nomura announced its intention to acquire Lehman Brothers' investment banking and equities businesses in Europe and the Middle East. The deal became effective on Monday, 13 October. In 2007, non-U.S. subsidiaries of Lehman Brothers were responsible for over 50% of global revenue produced.