Ultrafast modulation of electron-phonon couplings via laser excitation has been experimentally demonstrated, yet a clear microscopic understanding remains elusive. Here, we establish the first ab initio framework combining time-dependent density-functional theory, density-functional perturbation theory, and Migdal-Eliashberg theory to track electron-phonon couplings and superconductivity in prototypical phonon-mediated superconductor ${\mathrm{MgB}}_2$ under laser illumination. We find that near-infrared laser pulses induce charge transfer from boron $\sigma$ to $\pi$ orbitals, effectively renormalizing the electron-phonon couplings and boosting the superconducting critical temperature to $\sim 52\mathrm{K}$. The simulated thermalized superconducting gaps match well with experimental measurements. We propose a generalizable route for ultrafast modulation of superconductivity in materials whose dominant electron-phonon coupling channel can be selectively addressed by light, with photoinduced changes in electronic coupling and screening playing a central role. This Letter offers fundamental insight into nonequilibrium optical control of electron-phonon interactions and superconductivity, and provides a predictive tool for studying photo-modulated electron-phonon coupling and macroscopically observable superconducting properties.

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• Electron-phonon coupling
• Multiband superconductivity
• Ultrafast phenomena
• Type-II superconductors
• Eliashberg theory
• First-principles calculations
• Time-dependent DFT