• O'Brien, Michael
• O'Connell, Jack
• O'Connor, Brian
• O'Connor, Patrick
• O'Donnell, Anthony J
• O'Donnell, Pat
• O'Malley, Martin
• O'Neal, Michael
• O'Neil, Daniel
• O'Rourke, Jim
• Oakar, Mary Rose
• Oaks, Nathaniel T
• Obama, Barack
• Oberstar, James L
• Obey, David R
• Obrador, Andres Manuel Lopez
• Obuchowski, Michael
• Oder, G. Glenn
• Olmert, Ehud
• Olson, Donald
• Olson, Mark
• Oppenheimer, Suzi
• Oropeza, Jenny
• Orszag, Peter
• Ortiz, Deborah
• Ortiz, Felix
• Osborne, Tom
• Ose, Doug
• Osterman, Harry
• Owings III, George W.
• Oxley, Michael G