The Province of Caltanissetta (; Sicilian: Pruvincia di Nissa) is a province in the southern part of Sicily, Italy. It contains 22 comuni (singular: comune), which are listed at Comuni of the Province of Caltanissetta. Its coat of arms is a red crest and two green leaf stems on top with a laurel leaf on the right and a crown in the middle. The River Salso is the main river of the province; it is long and originates in the province of Palermo, and it flows into the Mediterranean in this province at the end of the Gulf of Gela.