| Altsasu/Alsasua | |
| Native Name: | Altsasu |
| Native Name Lang: | eu |
| Other Name: | Alsasua |
| Settlement Type: | Municipality |
| Coordinates: | 42.8953°N -2.1689°W |
| Pushpin Map: | Spain Navarre#Spain |
| Pushpin Map Caption: | Location of Altsasu/Alsasua within Navarre##Location of Altsasu/Alsasuawithin Spain |
| Subdivision Type: | Country |
| Subdivision Type1: | Autonomous community |
| Subdivision Type2: | Province |
| Subdivision Name2: | Navarre |
| Subdivision Type3: | Comarca/Eskualdea |
| Subdivision Name3: | La Barranca/Sakana |
| Leader Title: | Alcalde (Mayor) |
| Leader Name: | Javier Ollo Martínez[1] |
| Leader Party: | Geroa Bai |
| Area Total Km2: | 26.72 |
| Population Note: | (INE) |
| Population Density Km2: | auto |
| Population Demonym: | alsasuarra |
| Timezone: | CET |
| Utc Offset: | +1 |
| Timezone Dst: | CEST |
| Utc Offset Dst: | +2 |
| Postal Code Type: | Postal code |
| Postal Code: | 31800 |
Alsasua (in Spanish, Altsasu in Basque; official name: Altsasu/Alsasua) is a town located in the autonomous community of Navarre, northern Spain. Its population in 2017 was 7,419.[2] The Battle of Alsasua took place here in 1834. 30 years later the town turned into a railway hub, transforming its demography, economy, and cultural landscape. In 2016, a fight erupting in a bar escalated into an Audiencia Nacional judicial case that stirred the town.