The Diocese of Caltanissetta (Latin: Dioecesis Calatanisiadensis) is a Latin Church diocese of the Catholic Church in Sicily, It is a suffragan of the archdiocese of Agrigento.

[1] Caltanissetta once belonged to the diocese of Girgenti, but was created an episcopal see by Gregory XVI, in 1844.

At that time it was a suffragan of the archdiocese of Monreale.

The immense cavern of Caltabillotta is famous on account of the legend of a great dragon, driven away by the holy hermit Peregrinus when he chose that spot for a life of penance.

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