Gauge-gravity duality is an extremely useful tool for studying strongly-coupled gauge theories, and has many applications to real-world systems, such as the quark-gluon plasma and quantum critical points. Most gauge-gravity dualities involve a gauge theory with fields only in the adjoint representation of the gauge group. In many strongly-coupled systems, however, such as the quark-gluon plamsa, fields in the fundamental representation of the gauge group, 'flavor fields', are crucially important. For (3+1)-dimensional gauge theories with gravity duals (AdS5/CFT4), the supergravity description of flavor fields is well-understood: flavor fields appear in supergravity as probe D-branes in AdS5. The story for (2+1)-dimensional gauge theories (AdS4/CFT3) is much less developed. Indeed, for supergravity on AdS4 x S7, the dual (2+1)-dimensional field theory (without flavor) was only recently discovered. In this talk I will describe how to add flavor to this theory. In particular, I will present a general recipe to determine the field theory, and in particular the couplings of the flavor fields, given a probe D-brane in AdS4.