M99

M99 or M-99 may refer to:


 * Messier 99, an unbarred spiral galaxy approximately 60 million light-years away in the constellation Coma Berenices
 * Barrett M99, a sniper rifle
 * M-99 (Michigan highway), a state highway in Michigan
 * Etorphine (a.k.a. Immobilon or M99), a veterinary tranquilizer