  Context. Different theories have been developed to explain the origins and
properties of close-in giant planets, but none of them alone can explain all of
the properties of the warm Jupiters (WJs, Porb = 10 - 200 days). One of the
most intriguing characteristics of WJs is that they have a wide range of
orbital eccentricities, challenging our understanding of their formation and
evolution. Aims. The investigation of these systems is crucial in order to put
constraints on formation and evolution theories. TESS is providing a
significant sample of transiting WJs around stars bright enough to allow
spectroscopic follow-up studies. Methods. We carried out a radial velocity (RV)
follow-up study of the TESS candidate TOI-4515 b with the high-resolution
spectrograph HARPS-N in the context of the GAPS project, the aim of which is to
characterize young giant planets, and the TRES and FEROS spectrographs. We then
performed a joint analysis of the HARPS-N, TRES, FEROS, and TESS data in order
to fully characterize this planetary system. Results. We find that TOI-4515 b
orbits a 1.2 Gyr-old G-star, has an orbital period of Pb = 15.266446 +-
0.000013 days, a mass of Mb = 2.01 +- 0.05 MJ, and a radius of Rb = 1.09 +-
0.04 RJ. We also find an eccentricity of e = 0.46 +- 0.01, placing this planet
among the WJs with highly eccentric orbits. As no additional companion has been
detected, this high eccentricity might be the consequence of past violent
scattering events.
