Uranium ore deposits are economically recoverable concentrations of uranium within Earth's crust. Uranium is one of the most common elements in Earth's crust, being 40 times more common than silver and 500 times more common than gold. It can be found almost everywhere in rock, soil, rivers, and oceans. The challenge for commercial uranium extraction is to find those areas where the concentrations are adequate to form an economically viable deposit. The primary use for uranium obtained from mining is in fuel for nuclear reactors.

Globally, the distribution of uranium ore deposits is widespread on all continents, with the largest deposits found in Australia, Kazakhstan, and Canada. To date, high-grade deposits are only found in the Athabasca Basin region of Canada.^{[disputed – discuss]} Uranium deposits are generally classified based on host rocks, structural setting, and mineralogy of the deposit. The most widely used classification scheme was developed by the International Atomic Energy Agency and subdivides deposits into 15 categories.

Uranium is a silvery-gray, weakly radioactive metallic chemical element. It has the chemical symbol U and atomic number 92. The most common isotopes in natural uranium are ²³⁸U (99.274%) and ²³⁵U (0.711%). All uranium isotopes present in natural uranium are radioactive and fissionable, and ²³⁵U is fissile (will support a neutron-mediated chain reaction). Uranium, thorium, and one radioactive isotope of potassium (⁴⁰
K) as well as their decay products are the main elements contributing to natural terrestrial radioactivity. Cosmogenic radionuclides are of less importance, but unlike the aforementioned primordial radionuclides, which date back to the formation of the planet and have since slowly decayed away, they are replenished at roughly the same rate they decay by the bombardment of Earth with cosmic rays.

Uranium has the highest atomic weight of the naturally occurring elements and is approximately 70% denser than lead, but it is not as dense as tungsten, gold, platinum, iridium, or osmium. It is always found combined with other elements. Along with all elements having atomic weights higher than that of iron, it is only naturally formed in supernova explosions.

The primary uranium ore mineral is uraninite (UO₂) (previously known as pitchblende). A range of other uranium minerals can be found in various deposits. These include carnotite, tyuyamunite, torbernite and autunite. The davidite-brannerite-absite type uranium titanates, and the euxenite-fergusonite-samarskite group are other uranium minerals.

A large variety of secondary uranium minerals are known, many of which are brilliantly coloured and fluorescent. The most common are gummite (a mixture of minerals), autunite (with calcium), saleeite (magnesium) and torbernite (with copper); and hydrated uranium silicates such as coffinite, uranophane (with calcium) and sklodowskite (magnesium).

There are several themes of uranium ore deposit formation, which are caused by geological and chemical features of rocks and the element uranium. The basic themes of uranium ore genesis are host mineralogy, reduction-oxidation potential, and porosity.

Uranium is a highly soluble and radioactive heavy metal. It can be easily dissolved, transported and precipitated within groundwater by subtle changes in oxidation conditions. Uranium does not usually form very insoluble mineral species, which is a further factor in the wide variety of geological conditions and places in which uranium mineralization may accumulate.