Photocatalytic overall water splitting (OWS) is a promising route to alleviate the energy crisis and provide clean renewable energy. OWS using monolayers of transition metal dichalcogenides (TMDCs) has gained substantial interest due to their intriguing optoelectronic properties. However, TMDCs based OWS undergo high photo-corrosion in aqueous environment which hinder the hydrogen conversion efficiency and catalytic reactions. In this work, a pioneering first-principles screening of TMDCs monolayers were conducted, assessing their thermodynamic stability, solar to hydrogen (STH) conversion efficiency, stability in aqueous solution and catalytic activities. We have identified MoS2, MoSe2, WS2, and CrS2 monolayers in 2H phase, as well as PtSe2, PdSe2, and NiSe2 monolayers in 1T phase, to be highly stable in aqueous solution and efficient towards OWS. The screened TMDCs monolayers can effectively resist oxidative and reductive photo-corrosion in both acidic and alkaline environments. The oxidation and reduction potentials of the selected monolayers can be adjusted by tuning the pH level of the electrolyte to inhibit photo-corrosion. TMDCs monolayers have robust catalytic activities with low overpotentials of (0.31˗1.57) V for the oxygen and (0.19˗0.49) V for hydrogen evolutions. Moreover, the monolayers have high STH efficiencies such as MoS2 (10.4%), MoSe2 (16%), WS2 (11.1%), CrS2 (27.3%), PtSe2 (22.2%), PdSe2 (19.6%) and NiSe2 (20.1%), making them highly promising for commercial applications in hydrogen fuel conversion.