An ellipsometric method for the determination of emersed electrochemical interfacial thickness at metal electrodes is reported. To demonstrate the effectiveness of this technique, a series of layers on Ag electrodes emersed from aqueous electrolytes are characterized. For most electrolytes, the measured thickness of the emersed interface is consistent with separation of the interface from bulk solution just outside of the outer Helmholtz plane. This behavior is discussed in terms of the various forces involved in structuring the electrochemical interface.