Mark L. Attanasio is a Los Angeles investment management principal who, in September 2004, reached a deal, on behalf of an investment group, to purchase the Milwaukee Brewers from the family of Major League Baseball (MLB) commissioner Bud Selig for US$200 million. The deal was approved by MLB at the owners' winter meeting on January 13, 2005.

He is a senior executive with the money management firms TCW/Crescent Mezzanine and Trust Company of the West.

Attanasio was born on September 28, 1957 in The Bronx, New York and grew up in Tenafly, New Jersey, where he attended high school. He graduated from Brown University with a B.A. in 1979 and received his J.D. from Columbia Law School in 1982. He founded the Dallas investment firm Crescent Capital Partners in 1991, which was later bought by Trust Company of the West in 1995. In 2001, Attanasio joined the board of directors at the telecommunications firm Global Crossing, which filed for bankruptcy in January 2002. He resigned his position on the board shortly thereafter.

Along with Brewers Assistant General Manager Gord Ash and pitcher Ben Sheets, Attanasio is a part-owner of the Milwaukee Admirals.

Mark is the brother of television writer Paul Attanasio. 

His eldest son, Dan, and his band, Pan Am, have performed at Summerfest 2008 in Milwaukee, Wisconsin.

He was a major sponsor of the widely acclaimed Andy Warhol exhibition at the Milwaukee Art Museum.