Shock compression experiments on single crystal MnO grown by the Verneuil method have been carried out for the pressure range of 41-114GPa using both propellant and two-stage light-gas guns. The shock states, recorded with the inclined mirror method, were analyzed by the free-surface approximation and impedance-match solution. The observed shock compression curve of MnO with the rock salt structure(B1) is found to be slightly more compressible than that measured statically to 60GPa using a diamond-anvil cell. We observed a phase transition around 90GPa with a volume decrease of approximately 8%. The present phase transition pressure falls on a trend of B1-B2 (CsCl-type structure) transformation among alkaline earth metal monoxides, rather than transformation to the B8(NiAs-type structure) that w¿stite(FeO) demonstrates. ¿ American Geophysical Union 1996