This study introduces the concept of photophysical structured illumination velocimetry (PP-SIV), verified through comprehensive numerical simulations. PP-SIV can capture two-dimensional (2D) flow velocity fields from a single snapshot image of the emission pattern from luminescent probes, leveraging the suitable photodynamics of the probes and using the applied excitation field pattern as reference. By eliminating the need for any beam or sample scan, PP-SIV has the potential to significantly accelerate the data acquisition process required for velocity field imaging. Furthermore, with excitation patterns applied at different depths, three-dimensional (3D) flow imaging can be potentially achieved. We propose lanthanide-based upconversion nanoparticles (UCNPs), particularly those capable of both absorbing and emitting within the highly biocompatible and transparent NIR-II window (1000-1700 nm), as promising probe candidates for implementing PP-SIV. This concept holds significant potential to pave the way for rapid, three-dimensional (3D) blood flow imaging at sufficient speeds for real-time monitoring of hemodynamic events in the brain.