Grin

• A facial expression: see Smile
• Alexander Grin, (1880 - 1932) a Russian novelist
• GRIN (novel), a novel by Hungarian writer Béla Kasztovszky
• Grin (album), an album by the thrash metal band Coroner
• Grin (band), a band formed by Nils Lofgren
• Grin (Grin album), an album by the above band

GRIN may refer to:

• GRIN (company), a video game developer based in Sweden
• GriN bvba (company), an online-media developer based in Belgium ()
• GRIN, an acronym for gradient index: see Gradient index optics
• Great Images in NASA, a NASA-maintained collection of high-resolution aerospace related images
• Graph Reduction Intermediate Notation, an intermediate representation for lazy functional languages
• Grand Rapids Information Network, a public television channel
• Germplasm Resources Information Network, a software project
• Grand River Information Network, a Grand River Conservation Authority online mapping and data download tool ()