A system for filling balloons with lift gas is provided. The system includes apparatus for use with a balloon envelope of a balloon. This apparatus includes a main body having first and second portions. The first portion has a fill port and a hollow tube portion in communication with the fill port. The second portion has a surface and is insertable into a predefined opening in the balloon envelope. The surface of the second portion is configured to attach to an inner portion of the balloon envelope when the second portion is inserted in the predefined opening.
