Officers face charges including second-degree murder and manslaughter after the 25-year-old suffered a critical neck injury in the back of a police van, sparking violent unrest.
Baltimore’s Chief Prosecutor Marilyn Mosby said warrants had been issued for the arrest of the officers involved.
The charges against them range from murder and manslaughter to assault, misconduct and false imprisonment.
Gray was arrested on 12 April after running away from police, who found a knife in his pocket.
Ms Mosby said the knife was legal, no crime had been committed and the arrest was illegal as the officers had failed to establish probable cause.
They handcuffed Gray and placed him faced down in the back of a police van. He suffered a critical neck injury while riding in the van without restraints, in breach of police guidelines, the prosecutor said.
Gray had stopped breathing by the time he was removed from the police vehicle, she added.
Baltimore locals Ashley McDonald, Reverence Pamela Coleman and Joseph Kent give their reactions
His death on 19 April sparked violent protest amid ongoing anger over the treatment of black suspects by US police.
After a night of rioting in Baltimore on Monday, protests spread to other major US cities, recalling the demonstrations last year over police killings of unarmed black men in Ferguson, Missouri and New York.
Ms Mosby said Gray asked to be given an inhaler shortly after his arrest, and asked for medical treatment at least twice during the van ride to a police booking centre.
But officers failed to treat him, she said.
There were cheers from the crowd as Ms Mosby, a 35-year-old black woman who took office in January, announced the charges.
Some onlookers chanted: “Justice for Freddie!” and “Thank you, Ms Mosby.”
She began the press conference by saying she had met with the victim’s family, telling them: “No-one is above the law.”
Officer Caesar Goodson faces charges of “second-degree depraved heart murder”, involuntary manslaughter, second-degree assault, manslaughter by vehicle and misconduct in office.
Officer William Porter is charged with involuntary manslaughter, second-degree assault and misconduct in office.
Officer Brian Rice is charged with involuntary manslaughter, second-degree assault, misconduct in office and false imprisonment.
Officers Edward Nero and Garrett Miller are charged with second-degree assault, misconduct in office and false imprisonment.
Sgt Alicia White faces charges of involuntary manslaughter, second-degree assault and misconduct in office.