Giovanni Battista Donati (December 16 1826 – September 20 1873) was an Italian astronomer.

He discovered a number of comets, including the spectacular Comet Donati (C/1858 L1). He also pioneered spectroscopy of comets to determine their physical composition, discovering that the spectrum changed when a comet approached the Sun and heating caused it to emit its own light rather than reflected sunlight.

He began working at the observatory of Florence in 1852 and became its director in 1864.

Honors

• Donati crater on the Moon named for him.