Maureen Patricia O'Hara is an American financial economist. O'Hara is the Robert W. Purcell Professor of Management, a professor of finance, and Acting Director in Graduate Studies at the Samuel Curtis Johnson Graduate School of Management at Cornell University. She has won numerous awards and grants for her research, served on numerous boards, served as an editor for numerous finance journals, and chaired the dissertations of numerous students. In addition, she is well known as the author of Market Microstructure Theory. She was the first female president of the American Finance Association. She has been awarded honorary doctorates from three European universities. Research O'Hara's research focuses on issues in market microstructure, and she is the author of Market Microstructure Theory as well as numerous journal articles. Her most recent research has focused on high frequency market microstructure, bond market microstructure, the impact of transparency on trading system performance, listing and delisting issues in securities markets, block chains and cryptocurrencies, and the role of liquidity and information risk in asset pricing. She also works on issues in finance and ethics with her most recent book being Something for Nothing: Arbitrage and Ethics on Wall Street. In addition, O'Hara publishes widely on a broad range of topics including banking and financial intermediaries, law and finance, and experimental economics. Among O'Hara's numerous awards are the CFA Institute's James R. Vertin Award (2020), the American Finance Association 2000 Smith-Breeden Distinguished Paper Award for "When the Underwriter is the Market Maker: An Examination of Trading in the IPO Aftermarket" (with Katrina Ellis and Roni Michaely), 2002 Smith-Breeden Distinguished Paper Award for "Is Information Risk a Determinant of Asset Returns?" (with David Easley, and Soeren Hvidkjaer), and 2003 Smith-Breeden Distinguished Paper Award for "Presidential Address: Liquidity and Price Discovery." Prof. O'Hara is a co-inventor of the VPIN Flow Toxicity metric. Positions held O'Hara was the executive editor of the Review of Financial Studies (1999–2005). She has served as president of the Western Finance Association, and as president of the American Finance Association. O'Hara is on the board of trustees of TIAA and was a director of New Star Financial. She has also served as board chair of Investment Technology Group, Inc. (ITG). She has consulted for a number of companies and organizations, including Microsoft, Merrill Lynch, Credit Suisse First Boston, the New York Stock Exchange, Bristol-Myers Squibb, and the World Federation of Exchanges. O'Hara is an