The optical counterpart of the supersoft Small Magellanic Cloud transient pulsar RX~J0059.2-7138

We identify the probable optical counterpart of the SMC supersoft source, RX~J0059.2-7138, with a $\sim$~14th magnitude star lying within the X-ray error circle. We present high resolution optical spectroscopy, which reveals strong HI emission and HeI absorption, indicative of a Be star. This classification is consistent with the colours we derive from optical photometry. We thus find evidence to support the existing tentative identification of this object as a Be/X-ray binary, the first of its kind to exhibit luminous supersoft X-ray emission.