  We report the detection of a population of Wolf-Rayet (WR) stars in the
Sunburst Arc, a strongly gravitationally lensed galaxy at redshift $z=2.37$. As
the brightest known lensed galaxy, the Sunburst Arc has become an important
cosmic laboratory for studying star and cluster formation, Lyman $\alpha$
radiative transfer, and Lyman Continuum (LyC) escape. Here, we present the
first results of JWST/NIRCam imaging and NIRSpec IFU observations of the
Sunburst Arc, focusing on a stacked spectrum of the 12-fold imaged LyC-emitting
(Sunburst LCE) cluster. In agreement with previous studies, we find that the
cluster is massive and compact, with $M_{\text{dyn}} = (9\pm1) \times 10^{6}
M_{\odot}$, Our age estimate of 4.2--4.5 Myr is much larger than the crossing
time of $t_{\text{cross}} = 183 \pm 9 $ kyr, indicating that the cluster is
dynamically evolved and consistent with being gravitationally bound. We find a
significant nitrogen enhancement of the low ionization state ISM, with
$\log(N/O) = -0.74 \pm 0.09$, which is $\approx 0.8$ dex above typical values
for H II regions of similar metallicity in the local Universe. We find broad
stellar emission complexes around He II$\lambda 4686$ and C IV$\lambda 5808$
with associated nitrogen emission -- this is the first time WR signatures have
been directly observed at redshifts above $\sim 0.5$. The strength of the WR
signatures cannot be reproduced by stellar population models that only include
single-star evolution. While models with binary evolution better match the WR
features, they still struggle to reproduce the nitrogen-enhanced WR features.
JWST reveals the Sunburst LCE to be a highly ionized, proto-globular cluster
with low oxygen abundance and extreme nitrogen enhancement that hosts a
population of Wolf-Rayet stars, and possibly Very Massive stars (VMSs), which
are rapidly enriching the surrounding medium.
