Guasayán Department is a departamento of the province of Santiago del Estero, Argentina.

Its capital is San Pedro de Guasayán, with 1,715 inhabitants, located 124 kilometres from Santiago del Estero, the provincial capital, on Provincial Route 64.

[1] The highest peak in the department is Sinchi Caña at 630 metres, and no river issues from it.

[1] According to some historians, the term Guasayán could mean "path behind the sierra", or "view from the heights".

There are some ruins from Native American inhabitants, especially near Villa Guasayán.