  We study three-dimensional {\cal N}=2 U(N) Chern-Simons theory on S^3 coupled
to 2N_f chiral multiplets deformed by mass terms. The partition function
localizes to a matrix integral, which can be exactly computed in the large N
limit. In a specific decompactification limit, the theory exhibits quantum
(third-order) phase transitions at finite critical values of the coupling. The
theory presents three phases when 0 < N_f < N and two phases when N_f\geq N.
The vacuum expectation value of the supersymmetric circular Wilson loop has a
discontinuity in the first derivative.
