This paper is an introduction to and overview of the accompanying papers in this issue which give detailed results from the Galileo probe mission to Jupiter, including results from the Galileo orbiter and Earth-based observations that are relevant for understanding the probe data and placing them in context. A summary of prior knowledge of Jupiter's atmosphere is also presented. All probe scientific investigations were successful. As anticipated, the Galileo probe results confirm some expectations about Jupiter, refute others, and raise important new questions. The Galileo probe defined the atmospheric thermal structure at the probe entry site from ~1000 km above the 1 bar pressure level to a depth near 22 bars. During direct atmospheric sampling beginning near 0.4 bar, instruments on the probe measured composition, cloud properties, thermal structure, winds, radiative energy balance, and electrical properties of the Jovian atmosphere. Prior to reaching the Jovian atmosphere, probe instruments measured properties of the inner magnetosphere, observing regions not previously sampled by any spacecraft.