> ## Documentation Index
> Fetch the complete documentation index at: https://docs.wherobots.com/llms.txt
> Use this file to discover all available pages before exploring further.

# ST_Centroid

Returns the spherical centroid of a geography as a Geography point, computed on the sphere using S2:

* **Polygon / MultiPolygon** — area-weighted centroid via `S2Polygon.getCentroid()`.
* **LineString / MultiLineString** — length-weighted centroid via `S2Polyline.getCentroid()`.
* **Point / MultiPoint** — mean of the unit vectors.
* **GeographyCollection** — recursive weighted sum across the children.

The result is the unit-length centroid on the sphere. Unlike a planar (lon/lat) centroid, it is correct for antimeridian-crossing and high-latitude geographies. As with JTS for non-convex shapes, the centroid may lie outside the input geometry. Returns `NULL` when the centroid is undefined (empty geometry, or antipodal points whose unit vectors cancel).

## Signatures

```sql theme={"system"}
ST_Centroid (A: Geography)
```

## Parameters

<ParamField body="A" type="Geography" required>
  The geography whose spherical centroid is returned.
</ParamField>

## Return type

<ResponseField type="Geography">
  The centroid as a Geography point, or `NULL` when undefined.
</ResponseField>

## Example

```sql theme={"system"}
SELECT ST_AsEWKT(ST_Centroid(ST_GeogFromWKT('POLYGON ((0 0, 2 0, 2 2, 0 2, 0 0))')));
```

```
POINT (1 1)
```

For an antimeridian-crossing polygon, the spherical centroid stays on the antimeridian instead of jumping to the opposite side of the planet, which a planar centroid would do:

```sql theme={"system"}
SELECT ST_AsEWKT(ST_Centroid(ST_GeogFromWKT('POLYGON ((170 -1, -170 -1, -170 1, 170 1, 170 -1))')));
-- result: POINT near (180, 0) (or (-180, 0)), NOT (0, 0)
```