Enron Corporation was an American energy, commodities, and services company based in Houston, Texas. It was led by Kenneth Lay and developed in 1985 via a merger between Houston Natural Gas and InterNorth, both relatively small regional companies at the time of the merger. Before its bankruptcy on December 2, 2001, Enron employed approximately 20,600 staff and was a major electricity, natural gas, communications, and pulp and paper company, with claimed revenues of nearly $101 billion during 2000. Fortune named Enron "America's Most Innovative Company" for six consecutive years.

At the end of 2001, it was revealed that Enron's reported financial condition was sustained by an institutionalized, systematic, and creatively planned accounting fraud, known since as the Enron scandal. Enron became synonymous with willful, institutional fraud and systemic corruption. The scandal brought into question the accounting practices and activities of many corporations in the United States and was a factor in the enactment of the Sarbanes–Oxley Act of 2002. It affected the greater business world by causing, together with the even larger fraudulent bankruptcy of WorldCom, the dissolution of the Arthur Andersen accounting firm, which had been Enron and WorldCom's main auditor, and coconspirator in the fraud for years.

Enron filed for bankruptcy in the United States District Court for the Southern District of New York in late 2001 and selected Weil, Gotshal & Manges as its bankruptcy counsel. Enron emerged from bankruptcy in November 2004, under a court-approved plan of reorganization. A new board of directors changed its name to Enron Creditors Recovery Corp., and emphasized reorganizing and liquidating certain operations and assets of the pre-bankruptcy Enron. On September 7, 2006, Enron sold its last remaining subsidiary, Prisma Energy International, to Ashmore Energy International Ltd. (now AEI). It is the largest bankruptcy due specifically to fraud in United States history.

On December 2, 2024, the Enron website relaunched as satire, with Connor Gaydos, the cofounder of Birds Aren't Real, as CEO.

One of Enron's primary predecessors was InterNorth, which was formed in 1930, in Omaha, Nebraska, just a few months after Black Tuesday. The low cost of natural gas and the cheap supply of labor during the Great Depression helped to fuel the company's early beginnings, doubling in size by 1932. Over the next 50 years, Northern expanded even more as it acquired many energy companies. It was reorganized in 1979 as the main subsidiary of a holding company, InterNorth, a diversified energy and energy-related products firm. Although most of the acquisitions conducted were successful, some ended poorly. InterNorth competed with Cooper Industries unsuccessfully over a hostile takeover of Crouse-Hinds Company, an electrical products manufacturer. Cooper and InterNorth feuded in numerous suits during the takeover that were eventually settled after the transaction was completed. The subsidiary Northern Natural Gas operated the largest pipeline company in North America. By the 1980s, InterNorth became a major force for natural gas production, transmission, and marketing as well as for natural gas liquids, and was an innovator in the plastics industry. In 1983, InterNorth merged with the Belco Petroleum Company, a Fortune 500 oil exploration and development company founded by Arthur Belfer.

The Houston Natural Gas (HNG) corporation was initially formed from the Houston Oil Co. in 1925 to provide gas to customers in the Houston market through the building of gas pipelines. Under the leadership of CEO Robert Herring from 1967 to 1981, the company took advantage of the unregulated Texas natural gas market and the commodity surge in the early 1970s to become a dominant force in the energy industry. Toward the end of the 1970s, HNG's luck began to run out with rising gas prices forcing clients to switch to oil. In addition, with the passing of the Natural Gas Policy Act of 1978, the Texas market was less profitable and as a result, HNG's profits fell. After Herring died in 1981, M.D. Matthews briefly took over as CEO in a 3-year stint with initial success, but ultimately, a big dip in earnings led to his exit. In 1984, Kenneth Lay succeeded Matthews and inherited the troubled conglomerate.

With its conservative success, InterNorth became a target of corporate takeovers, the most prominent originating with Irwin Jacobs. InterNorth CEO Sam Segnar sought a friendly merger with HNG. In May 1985, Internorth acquired HNG for $2.3 billion, 40% higher than the current market price, and on July 16, 1985, the two entities voted to merge. The combined assets of the two companies created the second largest gas pipeline system in the US at that time. Internorth's north–south pipelines that served Iowa and Minnesota complemented HNG's Florida and California east-west pipelines well.

The company was initially named HNG/InterNorth Inc., even though InterNorth was technically the parent. At the outset, Segnar was CEO but was soon fired by the board of directors to name Lay to the post. Lay moved its headquarters back to Houston and set out to find a new name, spending more than $100,000 in focus groups and consultants in the process. Lippincott & Margulies, the advertising firm responsible for the InterNorth identity five years prior, suggested "Enteron". During a meeting with employees on February 14, 1986, Lay announced his interest in this name change, which would be held to a stockholder vote on April 10. Less than a month from this meeting, on March 7, 1986, a spokesman for HNG/InterNorth rescinded the planned Enteron proposal, as since its announcement the name had come under scrutiny for being the same as a medical term for the intestines. This same press release saw the introduction of the Enron name, which would be the new name voted on come April.