A new three PARAMETER Equation Of STATE (EOS) is developed based on well documented data, at three thermodynamic STATEs of the critical point, the normal bubble point and standard condition. Besides these STATEs, the EOS is designed to satisfy the condition of nearly zero Joule-Thomson (JT) coefficients at the normal boiling point. Critical properties and densities at the normal boiling point and a standard condition of more than 100 pure fluids were used. The new EOS is validated using experimental data and eight (8) of the popular EOSs, namely, SRK, PR, LLS, HK, MNM, SW, PT and ALS. The experimental data for pure fluids include 331 data points of vapor pressure covering 12 fluids and compressibility at the critical condition of 23 fluids. For mixtures, the data includes 129 PVT data points of 12 reservoir fluids [seven (7) of them are Sudanese crude oil considered for publication for the first time and five (5) from literature]. The new EOS is found to be superior to the existing EOSs in the prediction of PVT properties of mixtures with a grand average percent absolute deviation (AAPD) of 3.18%. It is also comparable to the existing EOSs in the prediction of vapor pressure despite the fact that existing EOSs are developed based on vapor pressure data; the grand average AAPD is 2.0. In terms of compressibility at the critical point with the exception of LLS, the new EOS yields better results than all other EOSs considered in this work.