  We study baryons in holographic QCD corresponding to 1+1 dimensional
single-flavor ($N_f$=1) QCD for the first time. We formulate 1+1 QCD using an
$S^1$-compactified D2/D8/$\overline{\rm D8}$ branes in the superstring theory,
and describe the baryon as a topological configuration in 1+1 $N_f$=1 QCD,
corresponding to $\Pi_1({\rm U(1)})={\bf Z}$. Unlike 1+3 QCD with $N_f \ge 2$,
however, we find that the low-dimensional baryonic soliton is generally
unstable against a scale transformation/variation and swells infinitely in 1+1
$N_f$=1 QCD at the leading of large $N_c$. We thus point out a serious
difficulty on the soliton picture of baryons in large $N_c$ in the
single-flavor world in both 1+1 and 1+3 QCD. We also compare the
low-dimensional holographic baryon with the Abrikosov vortex, i.e., a stable
topological configuration in Type-II superconductors.
