  We construct and study a new topological field theory in three dimensions. It
is a hybrid between Chern-Simons and Rozansky-Witten theory and can be regarded
as a topologically-twisted version of the N=4 d=3 supersymmetric gauge theory
recently discovered by Gaiotto and Witten. The model depends on a gauge group G
and a hyper-Kahler manifold X with a tri-holomorphic action of G. In the case
when X is an affine space, we show that the model is equivalent to Chern-Simons
theory whose gauge group is a supergroup. This explains the role of Lie
superalgebras in the construction of Gaiotto and Witten. For general X, our
model appears to be new. We describe some of its properties, focusing on the
case when G is simple and X is the cotangent bundle of the flag variety of G.
In particular, we show that Wilson loops are labeled by objects of a certain
category which is a quantum deformation of the equivariant derived category of
coherent sheaves on X.
