Outer mitochondrial membrane
The outer mitochondrial membrane is the outer membrane of the defining ingredient::mitochondrion, an organelle found in most eukaryotic cells. It is an example of a biological membrane. It comprises a lipid bilayer along with various integral membrane proteins embedded in that bilayer. It helps control the entry and exit of materials between the mitochondrion and the cytoplasm that surrounds it.
The mitochondrion also has an inner mitochondrial membrane which is also a lipid bilayer.