Atty. Gen. Eduardo Medina Mora stepped down after severe criticism from political opponents who said the government's drug war strategy was failing. Medina Mora will be sent abroad as ambassador, Calderon said, but he did not specify to which country.
Calderon praised Medina Mora as a "brave man" whose "professionalism and loyalty" had been instrumental in dealing what the president said was a significant blow to organized crime.
Medina Mora was a staunch defender of the government's strategy in targeting powerful drug cartels, despite numerous setbacks in the effort. The death toll has soared and victories have been elusive.
Medina Mora was also the go-to man in the Calderon administration for U.S. officials, who at times have had prickly relations with the Mexican government.
However, his long-rumored removal does not necessarily foreshadow major changes in the way the drug war will be fought, analysts said.
"The fight will no doubt be won by the Mexican state," Medina Mora said at a news conference announcing his resignation.
He will be replaced by Arturo Chavez Chavez, a little-known official from the federal prosecutor's office and member of Calderon's conservative National Action Party. The incoming attorney general hails from the violent border state of Chihuahua. The Senate has to ratify his appointment before he can assume the post.
More than 13,000 people have been killed since Calderon launched the offensive at the start of his administration in December 2006. More than 48,000 army troops and 5,000 federal police have been mobilized nationwide.
Not only has the campaign failed to turn up top fugitive drug kingpins and to stem the flow of illicit profits, but it also has led to allegations of human rights violations by the army and has exposed levels of corruption across the country, in police departments and local governments, as well as Medina Mora's own office.
Calderon also appointed Francisco Javier Mayorga Castaneda as the new agriculture minister, at a time when the nation is struggling with its worst drought since World War II, and Juan Jose Suarez Coppel as director of the state oil monopoly.