Valle Viejo is a central department of Catamarca Province in Argentina.
The provincial subdivision has a population of about 24,000 inhabitants in an area of , and its capital city is San Isidro.
The Valle Viejo region has been populated for at least 8,000 years. Around 1,000 years ago the area was settled by a population of farmers and hunters. The population created buildings, irrigation systems, and various fortifications.