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 \pm 2 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 .