2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/202549A fully non-perturbative lattice determination of the up/down and strange quark masses is given for quenched QCD using both, $O(a)$ improved Wilson fermions and ordinary Wilson fermions. For the strange quark mass with $O(a)$ improved fermions we obtain $m^{\msbar}_s(μ=2 {GeV}) = 105(4) {MeV}$, using the interquark force scale $r_0$. Due to quenching problems fits are only possible for quark masses larger than the strange quark mass. If we extrapolate our fits to the up/down quark mass we find for the average mass $m^{\msbar}_l(μ=2 {GeV}) = 4.4(2) {MeV}$.Latex, 25 pages, 12 eps figuresHigh Energy Physics - LatticeHigh Energy Physics - Phenomenologytext