Prosecutors in Siena accuse the 15 of beating and humiliating a prisoner in the San Gimignano jail last year, the Repubblica daily said. Four of the officers were suspended last week after a months-long probe.
The case against them reportedly draws on surveillance footage and witness statements from other prisoners.
Prison rights group Antigone said it was the first such case to be brought by prosecutors since torture was criminalised in 2017.
“Those who have seen abuse and violence must knock down the wall of silence” protecting perpetrators, the group's head Patrizio Gonnella said.
Unions warned in July that the situation at the San Gimignano jail was “explosive”, the Corriere della Sera daily said.