The process of exsolution for the synthesis of strongly anchored metal nanoparticles (NPs) on host oxide lattices has been proposed as a promising strategy for designing robust catalyst-support composite systems. However, because conventional exsolution processes occur in harsh reducing environments at high temperatures for long periods of time, the choice of support materials and dopant metals are limited to those with inherently high thermal and chemical stability. Herein, we report the exsolution of a series of noble metal catalysts (Pt, Rh, and Ir) from metal oxide nanofibers (WO3 NFs) supports in an entirely ambient environment induced by intense pulsed light (IPL)-derived momentary photothermal treatment (>1000 degrees C). Since the exsolution process spans an extremely short period of time (<20 ms), unwanted structural artifacts such as decreased surface area and phase transition of the support materials are effectively suppressed. At the same time, exsolved NPs (<5 nm) with uniform size distributions could successfully be formed. To prove the practical utility of exsolved catalytic NPs functionalized on WO3 NFs, the chemiresistive gas sensing characteristics of exsolved Pt-decorated WO3 NFs were analyzed, exhibiting high durability (>200 cyclic exposures), enhanced response (R-air/R-gas > 800 @ 1 ppm/350 degrees C), and selectivity toward H2S target gas. Altogether, we successfully demonstrated that ultrafast exsolution within a few milliseconds could be induced in ambient conditions using the IPL-derived momentary photothermal treatment and contributed to expanding the practical viability of the exsolution-based synthetic approaches for the production of highly stable catalyst systems.