MGN can refer to either:
- Mirror Group Newspaper chain of Trinity Mirror
- Medial geniculate nucleus: a subnucleus of the thalamus in the brain
- Membranous glomerulonephritis, a disease
- The Midland and Great Northern Joint Railway - (M&GN) - A former English Railway
- Mouettes Genevoises Navigation, public transportation by boat in Geneva, Switzerland
- Marston Green railway station, England; National Rail station code MGN.
- Military Grade Nano, a fictional use of Nanotechnology that is used to construct weapons for military use.