Which Austrian glacier is the longest glacier in Austria and the Eastern Alps?

The Austrian glacier that is the longest in Austria and the Eastern Alps is the Pasterze Glacier.

The Pasterze lies beneath Austria's highest mountain, the Grossglockner, in the Glockner Group of the High Tauern. It is approximately 8.4 kilometres long and forms part of the source region of the Möll River, whose waters eventually join the Drava.

The glacier begins near the Johannisberg peak at about 3,450 metres above sea level and descends to around 2,100 metres. It is within the High Tauern National Park and can be viewed from the Grossglockner High Alpine Road, making it one of Austria's best-known glaciers.

The Pasterze has changed dramatically since the nineteenth century. Its area was once more than 30 square kilometres, but modern measurements show a much smaller glacier, and the tongue continues to retreat. The Gepatschferner is another important Austrian glacier and may become larger than the Pasterze in the future, but it is not the current answer to the question asking for Austria's longest glacier.