  The pion decay constant $F_{\pi}$ plays an important role in QCD and in
Chiral Perturbation Theory. It is hardly known, however, that a corresponding
constant exists in the Schwinger model with $N_{\rm f} \geq 2$ degenerate
fermion flavors. In this case, the ``pion'' does not decay and $F_{\pi}$is
dimensionless. Still, $F_{\pi}$ can be defined by 2d analogies to the
Gell-Mann--Oakes--Renner relation, the Witten--Veneziano formula and the
residual ``pion'' mass in the $\delta$-regime. With suitable assumptions, and
by inserting simulation data, these QCD-inspired relations are all compatible
with $F_{\pi} \simeq 1/\sqrt{2\pi}$ at zero fermion mass, as we observe for
$N_{\rm f} = 2, \dots , 6$. We conclude that this is a meaningful constant in
the multi-flavor Schwinger model.
