A search for the direct production of charginos and neutralinos in final states with three leptons and missing transverse momentum is presented. The analysis is based on 20.3 fb −1 of √s = 8 TeV proton-proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with the Standard Model expectations and limits are set in R -parity-conserving phenomenological Minimal Supersymmetric Standard Models and in simplified supersymmetric models, significantly extending previous results. For simplified supersymmetric models of direct chargino $ \left( {\widetilde{\chi}_1^{\pm }} \right) $ and next-to-lightest neutralino $ \left( {\widetilde{\chi}_2^0} \right) $ production with decays to lightest neutralino $ \left( {\widetilde{\chi}_1^0} \right) $ via either all three generations of sleptons, staus only, gauge bosons, or Higgs bosons, $ \left( {\widetilde{\chi}_1^{\pm }} \right) $ and $ \left( {\widetilde{\chi}_2^0} \right) $ masses are excluded up to 700 GeV, 380 GeV, 345 GeV, or 148 GeV respectively, for a massless $ \left( {\widetilde{\chi}_1^0} \right) $ .