In chemistry, trigonal planar is a molecular geometry with one atom at the center and three atoms at the corners of a triangle all in one plane. In a nonpolar molecule all the bond angles are 120°, although polar molecules - such as H₂CO - will deviate from this ideal geometry. In general the atomic orbitals of a trigonal planar molecule are sp² hybridized. Examples of molecules with a trigonal planar geometry are boron trifluoride and formaldehyde.

Pyramidalization is a distortion of this molecular shape towards a tetrahedral molecular geometry. One way to observe this distortion is in pyramidal alkenes.

Stereochemistry | Molecular geometry