An apparatus for illuminating the interior of a balloon includes a
cylindrical plug with an integrally-formed radially extending integral
flange insertable within the balloon neck. A light element is affixed to
the plug and disposed within the neck. A battery is electrically
connected to the light element and is typically mounted next to the light
element, or includes the light element in a single assembly. Switching is
provided to turn the lighting element on and off which, in the preferred
embodiment is effected by inflating the balloon with the apparatus
inserted into the balloon neck. The light element may be affixed to the
head of the apparatus by magnetic means, by means of a screw-on cap, or
by other well-known techniques.