Murphy is the second-longest serving mayor in the city, which is more than 200 years old. At a news conference Tuesday announcing his plans, Murphy said: "It was really a personal decision on my part. I'm 60 years old and there's lots of things I want to do with my life."
Murphy is best known for pushing economic development projects -- with mixed results -- trying to keep Pittsburgh solvent. Last year he began to combat economic problems, which saw the city's bond status downgraded to junk and laid off hundreds of city workers, the Pittsburgh Post-Gazette reported.
The mayor said he would serve out the rest of his current term, giving him 12 years in office. Only David L. Lawrence, Pittsburgh mayor from 1944-58, served in the office longer.
The Post-Gazette said those considered early frontrunners -- although none has announced a mayoral run -- to replace Murphy include former City Council President Bob O'Connor, City Councilman William Peduto, Allegheny County Prothonotary Michael Lamb, city Controller and county Democratic Party Chairman Tom Flaherty.
Megyn Kelly: Santa Claus and Jesus are both white men
Penelope Cruz named 2013's 'Best Body' by Fitness magazine