The coupling between electronic excitations and collective bosonic modes is fundamental to the emergence of high-temperature superconductivity in cuprates. Despite extensive effort, conventional equilibrium and pump–probe optical spectroscopies still struggle to disentangle couplings to different bosonic modes when their energy scales overlap. Here we overcome this limitation using ultrafast two-dimensional electronic spectroscopy (2DES), which correlates excitation and detection photon energies with femtosecond time resolution. Applied to optimally doped Bi2212, 2DES reveals a pronounced off-diagonal resonance arising from the ultrafast generation of nonthermal bosons with energy ℏΩq = 200 meV. By comparing the measured spectra with a theoretical framework that explicitly includes the interaction between charge-transfer and magnetic excitations, we identify these bosons as paramagnons with momenta centered near (π/2, π/2) and extending toward (0, π) and (π, 0). The resonance persists across a large range of temperatures and doping concentrations, demonstrating that high-energy paramagnons are ubiquitously and strongly coupled to electronic excitations throughout the cuprate phase diagram. Time-domain analysis constrains the build-up of the paramagnon population to ≲ 10 fs, placing a lower bound λ ≳ 0.7 on the coupling strength. More broadly, our results establish 2DES as a powerful approach for disentangling mode-selective electron–boson interactions in strongly correlated materials.