Andrew Stuart Fastow (born 22 December 1961) was the chief financial officer of Enron Corporation that was based in Houston, Texas until the U.S. Securities and Exchange Commission opened an investigation into his and the company's conduct in 2001. Fastow was one of the key figures behind the complex web of off-balance-sheet special purpose entities (limited partnerships which Enron controlled) used to conceal their massive losses. Fastow is serving a six-year prison sentence for charges related to these unlawful acts.