In crystallography, the orthorhombic crystal system is one of the 7 lattice point groups. Orthorhombic lattices result from stretching a cubic lattice along two of its lattice vectors by two different factors, resulting in a rectangular prism with a rectangular base (a by b, which is different from a) and height (c, which is different from a and b). The three lattice vectors remain mutually orthogonal.

There are four orthorhombic Bravais lattices: simple orthorhombic, base-centered orthorhombic, body-centered orthorhombic, and face-centered orthorhombic.

simple orthorhombic	base-centered orthorhombic	body-centered orthorhombic	face-centered orthorhombic

The point groups (or crystal classes) that fall under this crystal system are listed below, followed by their representations in international notation and Schoenflies notation, and mineral examples.

name	international	Schoenflies	example
orthorhombic bipyramidal		D2h	sulfur
orthorhombic pyramidal	2mm	C2v
orthorhombic sphenoidal	222	D2