  We develop a hydrodynamic field theory of the three-dimensional fractional
quantum Hall effect, which was recently proposed to exist in magnetic Weyl
semimetals, when the Weyl nodes are gapped by strong repulsive interactions.
This theory takes the form of a BF theory, which contains both one-form and
two-form gauge fields, coupling to quasiparticle and loop excitations
correspondingly. It may be regarded as a generalization of the Chern-Simons
theory of two-dimensional fractional quantum Hall liquids to three dimensions.
