| Official Name: | Gaztelu |
| Pushpin Map: | Spain Basque Country#Spain |
| Pushpin Map Caption: | Location of Gaztelu within the Basque Country |
| Coordinates: | 43.1164°N -2.0228°W |
| Subdivision Type: | Country |
| Subdivision Name: | Spain |
| Subdivision Type1: | Autonomous community |
| Subdivision Name1: | Gipuzkoa |
| Subdivision Type2: | Province |
| Area Total Km2: | 9.15 |
| Population Density Km2: | auto |
| Timezone: | CET |
| Utc Offset: | +1 |
| Timezone Dst: | CEST |
| Utc Offset Dst: | +2 |
Gaztelu is a village and municipality located in the province of Gipuzkoa, in the autonomous community of Basque Country, northern Spain.