Ioannis G. Papadakis (1820 - 1876 Greek: Ιωάννης Παπαδάκης) was an author, mathematician, physicist, astronomer, meteorologist, and professor. He was the second director of the National Observatory of Athens. He temporarily succeeded Georgios Konstantinos Vouris until Johann Friedrich Julius Schmidt replaced him as the third director of the observatory. His most notable work was the observation of the Moons of Jupiter and other meteorological observations in the 1850s. He was also a Scottish rite freemason.