  We have used long-baseline near-IR interferometry to resolve the peculiar
eruptive variable V838 Mon and to provide the first direct measurement of its
angular size. Assuming a uniform disk model for the emission we derive an
apparent angular diameter at the time of observations (November-December 2004)
of $1.83 \pm 0.06$ milli-arcseconds. For a nominal distance of $8\pm2$ kpc,
this implies a linear radius of $1570 \pm 400 R_{\odot}$. However, the data are
somewhat better fit by elliptical disk or binary component models, and we
suggest that the emission may be strongly affected by ejecta from the outburst.
