| Saín Alto | |
| Settlement Type: | City & municipal seat |
| Mapsize: | 300px |
| Pushpin Map: | Mexico Zacatecas#Mexico |
| Pushpin Label Position: | above |
| Pushpin Mapsize: | 300 |
| Pushpin Map Caption: | Location of Saín Alto |
| Subdivision Type: | Country |
| Subdivision Name: |  Mexico |
| Subdivision Type1: | State |
| Subdivision Name1: | Zacatecas |
| Subdivision Type2: | Municipality |
| Subdivision Name2: | Saín Alto |
| Leader Title: | Municipal President |
| Established Title: | Founded |
| Established Date: | 1555 |
| Established Title2: | City status |
| Population As Of: | 2020 |
| Population Total: | 5,295 |
| Population Blank1 Title: | Ethnicities |
| Population Blank2 Title: | Religions |
| Coordinates: | 23.5811°N -103.2481°W |
| Elevation M: | 2,045 |
| Postal Code Type: | Postal code |
| Area Code: | 498 |
| Blank Name: | Demonym |
Sain Alto is a locality in the Mexican state of Zacatecas. It serves as the municipal seat of the eponymous Sain Alto Municipality.
Saín Alto has a cold steppe climate.[1] The average annual temperature in the town is 21C. The warmest month is May, with an average temperature of 29C, and the coldest is January, at 14C.[2] Average annual rainfall is . The wettest month is September, with an average of of precipitation, and the driest is March, at .[3]
Saín Alto derives from or Çayn,[4] a group of Zacateco people who established the settlement of Saín Alto sometime around 1535–1540. These people were led by a cacique named Saín Alonso. The town's full name was originally "San Sebastián con el renombre de Saín", but it eventually became known as San Sebastián de Saín Alto and later simply Saín Alto. The earliest Spanish conquistadors to come into contact with the people of Zaín were in 1552 and 1553, and Francisco de Ibarra in September 1554.[5]
With the first Zacatecas state constitution of 1825, Saín Alto became the seat of its own municipality. The latter became a free municipality on 19 August 1916.[5] [6] Mercury mining began in the municipality in 1934, and accounted for 12% of Mexico's mercury production in the years of 1939 and 1940.[5]
In the 2020 Mexican Census, Saín Alto recorded a population of 5,295 inhabitants.[7]