We briefly review femtosecond laser induced chemical reactions and nanomaterial productions in a liquid phase. Focused intense femtosecond laser pulses create a high density of reactive species such as solvated electrons and cation radicals of the solvent. The solvated electrons efficiently reduce the metal ions followed by their nanoparticle formations. Multimetallic nanoparticles, which are expected to be utilized as electromagnetic materials and catalysts, are produced. In the cases of neat organic solvents, polyynes and carbon nanoparticles are formed. We also presented the production of heteroatom-doped carbon nanoparticles, which are candidates of oxygen reduction catalysts in fuel cells. By using aqueous organic solutions and/or water/organic bilayer solutions, hydrophilic carbon nanoparticles are formed by the successive oxidation of organic molecules by hydroxyl radicals. Nanoparticle synthesis by reactive species in the liquid phase might be an alternative means of widely used laser ablation in liquid.