| Guasayán Department | |
| Native Name Lang: | es |
| Settlement Type: | Department |
| Mapsize: | 180px |
| Pushpin Map Caption: | Location of Guasayán Department in Argentina |
| Coordinates: | -27.95°N -75°W |
| Coor Pinpoint: | San Pedro |
| Subdivision Type: | Country |
| Subdivision Name: |  Argentina |
| Subdivision Type1: | Province |
| Subdivision Name1: | Santiago del Estero |
| Seat Type: | Head town |
| Seat: | San Pedro de Guasayán |
| Unit Pref: | Metric |
| Area Total Km2: | 2588 |
| Population Total: | 7404 |
| Population Density Km2: | auto |
| Timezone1: | ART |
| Utc Offset1: | -3 |
Guasayán Department is a departamento of the province of Santiago del Estero, Argentina.
This region of small mountains in the west of the province is 2,588 km² (less than 2% of the province) and has 7,404 inhabitants (less than 1% of the province's population). 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. Other villages include Lavalle, Guampaya and Villa Guasayán.[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. Diego de Rojas is said to have travelled through those lands around 1544.[2]