In this seminar I will discuss monopole operators in the context
of supersymmetric gauge theories in three dimensions and the role they
play in establishing new infrared dualities. Using then a recently
proposed duality for U(N) supersymmetric QCD (SQCD) in three dimensions
with monopole superpotential, I will derive the mirror dual description of
N=2 SQCD with unitary gauge group, generalizing the known dual description
of abelian gauge theories.