Noncommutative geometry, matrices and string theory

This thesis is a study of several aspects of noncommutative geometry arising in the context of string theory and field theories. The first chapter contains a brief introduction to noncommutative geometry, surveying relevant topics in string theory and exploring the connections between noncommutative geometry and string theory. Four different topics are then studied in depth: the noncommutative model of the D1-D3 brane intersection in a background magnetic field, intersecting solitons and their fluctuations in noncommutative scalar field theory, gravity duals of nonlocal field theories, and the M(atrix) model for the noncommutative deformation of the (2,0) theory on the five-brane.