Structural geology is the branch of earth sciences that deals with the geological processes through which the application of a force results in the transformation of a shape, arrangement or internal fabric of the rock into another shape, arrangement or internal fabric. This transformation is called deformation. For example, a planar layer may be bent (folded) or torn apart (faulted). Folds and faults are the two main groups of structures concerned by structural geology. Fracture patterns within the rock layers are another important structural feature.

The study of geologic structures has been of prime importance in economic geology, both petroleum geology and mining geology . Folded and faulted rock strata commonly form traps for the accumulation and concentration of fluids such as petroleum and natural gas. Faulted and structurally complex areas are notable as concentration areas for base and precious metal deposits. Veins of minerals containing various metals commonly occupy faults and fractures in structurally complex areas. These structurally fractured and faulted zones often occur in association with intrusive igneous rocks. They often also occur around geologic reef complexes and collapse features such as ancient sinkholes. Deposits of gold, silver, copper, lead, zinc, and other metals, are commonly located in structurally complex areas.

Environmental geologists and engineering geologists are also very interested in geologic structures. Obviously regions of active faulting and other active or recently active seismic areas are of prime concern. In addition areas of karst landscapes which are underlain by underground caverns and potential sinkholes or collapse features are of importance for these scientists. In addition, areas of steep slopes are potential collapse or landslide hazards. The internal structures and orientation of these structures are of critical imprtance when working in steep terranes for example roadcuts in highway construction.

Tectonics is structural geology on a large scale, usually referring to the structural effects of continental collisions and other plate tectonic features.

See also Important publications in structural geology