Meehan, named by President Bush as chief prosecutor for the Eastern District of Pennsylvania nearly seven years ago, didn't immediately reveal the reason for his departure. He scheduled a news conference for Monday afternoon.
The Republican has been mentioned as a possible candidate for governor in 2010.
Meehan was sworn into his current post in 2001, only six days after the Sept. 11 terrorist attacks. He oversees an office of some 200 lawyers who handle all the civil and criminal federal cases in Philadelphia and eight other southeastern Pennsylvania counties.
Meehan's tenure saw more than a dozen convictions stemming from a federal probe that became public when police discovered an FBI bug in then-Mayor John F. Street's office in October 2003. Street was never charged, but several confidants and the city treasurer were put away.
Meehan's office is also prosecuting one of the state Senate's most powerful figures, outgoing Democratic Sen. Vincent Fumo.
His office has named among its priorities the protection of children from online predators and the elderly from substandard nursing homes and predatory lenders. Other initiatives have include prosecuting identity theft and cracking down on gang activity.
Meehan was elected Delaware County district attorney in 1995.
A month into his tenure there, he was thrust into the prosecution of high-profile murder suspect John DuPont. Heir to his family's chemical fortune, DuPont was convicted of the 1996 shooting death of Olympic gold medal-winning wrestler David Schultz.
Meehan received his undergraduate degree from Bowdoin College, where he was a hockey standout, and was a National Hockey League on-ice official for several years.
He graduated from Temple University law school. Before becoming a prosecutor, he worked as a corporate lawyer and an aide to U.S. Sen. Arlen Specter, R-Pa.
He ran high-profile statewide election campaigns including Specter's 1992 Senate win and U.S. Sen. Rick Santorum's upset victory in 1994.
On the Net:
Meehan bio: http://www.usdoj.gov/usao/pae/usa.html
