The gal (symbol: Gal), sometimes called galileo after Galileo Galilei, is a unit of acceleration typically used in precision gravimetry.

The milligal (mGal) and microgal (μGal) are respectively one thousandth and one millionth of a gal.

The gal is not part of the International System of Units (known by its French-language initials "SI").

Mountains and masses of lesser density within the Earth's crust typically cause variations in gravitational acceleration of tens to hundreds of milligals (mGal).

The gravity gradient (variation with height) above Earth's surface is about 3.1 μGal per centimeter of height (3.1×10−6 s−2), resulting in a maximal difference of about 2 Gal (0.02 m/s2) from the top of Mount Everest to sea level.