  We consider topological defect lines (TDLs) in two-dimensional fermionic
conformal field theories (CFTs). Besides inheriting all the properties of TDLs
in bosonic CFTs, TDLs in fermionic CFTs could host fermionic defect operators
at their endpoints and junctions. Furthermore, there is a new type of TDLs,
called q-type TDLs, that have no analog in bosonic CFTs. Their distinguishing
feature is an extra one-dimensional Majorana fermion living on the worldline of
the TDLs. The properties of TDLs in fermionic CFTs are captured in the
mathematical language of the super fusion category. We propose a classification
of the rank-2 super fusion categories generalizing the $\mathbb Z_8$
classification for the anomalies of $\mathbb Z_2$ symmetry. We explicitly solve
the F-moves for all the nontrivial categories, and derive the corresponding
spin selection rules that constrain the spectrum of the defect operators. We
find the full set of TDLs in the standard fermionic minimal models and a
partial set of TDLs in the two exceptional models, which give CFT realizations
to the rank-2 super fusion categories. Finally, we discuss a constraint on the
renormalization group flow that preserves a q-type TDL.
