Spectra of K-S(0) mesons and Lambda hyperons were measured in p + C interactions at 31 GeV/c with the large acceptance NA61/SHINE spectrometer at the CERN SPS. The data were collected with an isotropic graphite target with a thickness of 4% of a nuclear interaction length. Interaction cross sections, charged pion spectra, and charged kaon spectra were previously measured using the same data set. Results on K-S(0) and Lambda production in p + C interactions serve as a reference for the understanding of the enhancement of strangeness production in nucleus-nucleus collisions. Moreover, they provide important input for the improvement of neutrino flux predictions for the T2K long baseline neutrino oscillation experiment in Japan. Inclusive production cross sections for K-S(0) and Lambda are presented as a function of laboratory momentum in intervals of the laboratory polar angle covering the range from 0 up to 240 mrad. The results are compared with predictions of several hadron production models. The K-S(0) mean multiplicity in production processes < n(KS0)> and the inclusive cross section for K-S(0) production sigma(KS0) were measured and amount to 0.127 +/- 0.005 (stat) +/- 0.022 (sys) and 29.0 +/- 1.6 (stat) +/- 5.0 (sys) mb, respectively.
