  The NOvA long-baseline neutrino experiment uses a pair of large, segmented,
liquid-scintillator calorimeters to study neutrino oscillations, using
GeV-scale neutrinos from the Fermilab NuMI beam. These detectors are also
sensitive to the flux of neutrinos which are emitted during a core-collapse
supernova through inverse beta decay interactions on carbon at energies of
$\mathcal{O}(10~\text{MeV})$. This signature provides a means to study the
dominant mode of energy release for a core-collapse supernova occurring in our
galaxy. We describe the data-driven software trigger system developed and
employed by the NOvA experiment to identify and record neutrino data from
nearby galactic supernovae. This technique has been used by NOvA to
self-trigger on potential core-collapse supernovae in our galaxy, with an
estimated sensitivity reaching out to 10~kpc distance while achieving a
detection efficiency of 23\% to 49\% for supernovae from progenitor stars with
masses of 9.6\~M$_\odot$ to 27\~M$_\odot$, respectively.
