The 5,10,15,20-tetra(4-nitrophenyl)porphyrin (TNPP) has been synthesized using the reaction of pyrrole and 4-nitrobenzaldehyde in the presence of propionic acid. The TNPP was used as a new fluorescent chemosensor to determine Ru3+ with higher selectivity than other ions such as Hg2+, CH3Hg+, Ag+, Co2+, Cd2+, Ni2+, Cr3+, Fe3+, Cu2+, or Zn2+. The response of the new chemosensor is reported in the form of fluorescence quenching, which is attributed to the metalloporphyrin formation of Ru-TNPP complex with 1:1 stoichiometric ratio (K-stab = 2.04 x 10(8)). The synthesized fluorescence chemosensor can be used to determine Ru3+ with a detection limit of 0.89 mu M (90 ppb) and a linear quantification range between 3 and 25 mu M. Therefore, the synthesized chemosensor could be used as a new fluorescence chemosensor for the quantitative analysis of Ru3+ with satisfactory results