Abstract: An immersible liquid densitometer is disclosed employing an immersible vibrator. The vibrator includes one or two masses which are resiliently supported and which contain perforations which fill when the vibrator is immersed in the liquid. When the vibrator is immersed, the frequency of vibration is affected in proportion to the density of the liquid filling the perforations. Thus, measurement of the frequency of vibration may be used to determine the density of the immersing liquid. For maximum accuracy, the configuration and vibratory mode of the masses are selected for minimum energy coupling to the liquid. Typically, a cylindrical configuration is selected vibrating in a rotational mode. Under these conditions, the drag during vibration is due primarily to skin friction and a high Q, high accuracy measurement is achieved.