Haitiian President Michel Martelly honored Penn with the title at a ceremony on Tuesday at the National Palace.
The actor was honored for all his humanitarian work since the devastating earthquake of 2010. Martelly thanked Penn for keeping the spotlight on the still recovering Caribbean nation.
Penn's J/P Haitian Relief Organization was set up a few months after the Jan. 12, 2010, earthquake to oversee a settlement camp where thousands of people displaced by the disaster lived.
The Associated Press contributed to this report.