Thomas Middelhoff (born May 11, 1953) is a former German corporate manager. He was on the board of directors of Bertelsmann from 1990–2002, being CEO from 1998. From 2004 to 1 March 2009, Middelhoff was chairman of the supervisory board of Arcandor (previously KarstadtQuelle AG), and CEO of the company.
Thomas Middelhoff was born in Düsseldorf, Germany, the son of a textile businessman. He studied business at the University of Münster and received his doctorate at the Institute for Marketing under the supervision of Heribert Meffert. While at university, he was already working in his father's textile business. After graduating he was given a high post in the company.
In 1986 he moved to Bertelsmann, a multinational media corporation based in Germany, as assistant manager of the graphic firm in Gütersloh. In 1990, he became a member of the board of directors of Bertelsmann.
Middelhoff recognized the potential of the new digital media early. He made small investments into Firma Pixelpark in Berlin among others, on Bertelsmann's behalf. As an early believer in the rapid development of the Internet, he suggested a large financial participation of Bertelsmann in America Online (AOL) when it was still a young company, and created the joint venture AOL Europe, with a financial holding of $50 million for a 5% stake. This investment was extremely successful and would later influence Middelhoff's ascent in the company to chairman of the board. In May 1995, he became a member of the governing board of AOL, and during his time in this position Middelhoff became a "close friend" of AOL's founder, Steve Case.
In 1995, Bertelsmann and AOL started the joint venture AOL Germany. From November 1998 to July 2002, Middelhoff was the CEO of Bertelsmann. During this time it increased its internet activities by starting the online media portal BOL (Bertelsmann Online), which was sold to buch.de in 2002. But Bertelsmann soon stepped back from these online engagements, selling its shares of AOL-Europe back to Time Warner, which had merged with AOL in 2001. In January 2000 Middelhoff declined a directorship at AOL and resigned from the supervisory board of the corporation.