This volume presents the proceedings of a workshop on geometry, topology, and markets held at The Fields Institute. The workshop was attended by eminent mathematicians and financial and economic theorists. Using a topological approach, the volume discusses new mathematics and its applications to social sciences and financial markets. Topics addressed at the workshop included new topological invariants for existence, characterization and computation of market equilibria and their relation to social choice and to other forms of resource allocation, competitive and cooperative systems, algebraic geometry and markets with increasing returns, computational complexity, and stochastic processes and financial markets.