ST_MinimumBoundingCircle

Introduction: Returns the smallest circle polygon that contains a geometry.

Format: ST_MinimumBoundingCircle(geom: geometry, [Optional] quadrantSegments:int)

Return type: Geometry

SQL example:

SELECT ST_MinimumBoundingCircle(ST_GeomFromText('POLYGON((1 1,0 0, -1 1, 1 1))'))