Title: Representations of vertex operator algebras, open-closed conformal field theories and string field theory Abstract: For a vertex operator algebra V satisfying certain natural positive-energy, reductivity and finiteness conditions, the category of V-modules has been shown by me to have a natural modular tensor category structure in the sense of Turaev. Open-closed conformal field theories containing V have been shown by Kong and me in a series of papers to be equivalent to pairs consisting of a noncommutative Frobenius algebra and a commutative Frobenius algebra in suitable modular tensor categories satisfying additional natural conditions. This formulation and the corresponding construction of open-closed conformal field theories provide a natural and general framework for the study of string field theory. For example, Witten's star product in open string field theory is nothing but the product for noncommutative Frobenius algebras in the category of V-modules and Witten's open string field action can be formulated and studied using the representation theory of V.