A comprehensive study of Vatnajökull outlet glaciers in Austur-Skafafellsýsla from 1600s to present has been conducted by gathering data from the rich historical archives of the county, historical oblique photographs, geographical maps and glacial geomorphological field evidence such as moraines at the glacier‘s maximum extent at the end of 19th century. In addition, maps, aerial and repeat photographs, satellite images and LiDAR (laser scanning) digital elevation model record the shape and position of the glaciers in the period 1904-2010. This is likely among the data-richest places for this kind of study, which is the warmest and wettest area in Iceland, causing the outlet glaciers to respond rapidly to changes in climate. The size and shape of ten outlet glaciers at the end of the cold period that has been called the Little Ice Age (LIA) was reconstructed based on these data. From this data set, area and volume changes 1890-2010 are deduced, and the average geodetic specific mass balance estimated for several time periods. The area of the individual outlet glacier has reduced by 10-30% since the maximum extent in 1890 while the total area reduction is 164 km2. The volume loss of individual outlet glaciers is in the range of 15–50%, with total volume loss of 60 km3, equivalent to 0.15 ± 0.02 mm mean sea level rise. The mean geodetic mass balances in the period 1890-2010 was –0.7 to –0.3 m w.e. a-1. The most negative mass balance is observed between 2002 and 2010, when the glaciers lost –2.6 to –0.8 m w.e. a-1 (or -1.34 m w.e. a-1 on average) among the highest rate in the world. A coupled ice flow and mass balance model successfully simulated the observed response of the glaciers to changes in temperature and precipitation. Sensitivity study with this model indicates that increase in temperature of 2-3 °C until 2100 will lead to a total volume loss of 50-80% in this area.