The nonlinear-opticar properties of Prussian Blue nanoparticles have been evaluated with the use of femtosecond Z-scan measurements in the 1350-1750 nm range. This well-known inorganic pigment having interesting magnetic and electrochemical properties was found to be an efficient near-IR three-photon absorber. The maximum of the effective three-photon cross section is as high as 4.5 x 10(-78) cm(6) s(2) at 1375 nm. By a comparison of the three-photon molar-mass-normalized merit factors, sigma(3)/M, we show that this, material is a competitive multiphoton absorber, especially in comparison to semiconductor quantum dots.