Context : The young \sigma Orionis cluster is an important location for understanding the formation and evolution of stars , brown dwarfs , and planetary-mass objects .
Its metallicity , although being a fundamental parameter , has not been well determined yet .

Aims : We present the first determination of the metallicity of nine young late-type stars in \sigma Orionis .

Methods : Using the optical and near-infrared broadband photometry available in the literature we derive the effective temperatures for these nine cluster stars , which lie in the interval 4300–6500 K ( 1–3 \hbox { M } _ { \odot } ) .
These parameters are employed to compute a grid of synthetic spectra based on the code MOOG and Kurucz model atmospheres .
We employ a \chi ^ { 2 } -minimization procedure to derive the stellar surface gravity and atmospheric abundances of Al , Ca , Si , Fe , Ni and Li , using multi-object optical spectroscopy taken with WYFFOS+AF2 at at the William Herschel Telescope ( \lambda / \delta \lambda \sim 7500 ) .

Results : The average metallicity of the \sigma Orionis cluster is [ Fe/H ] = -0.02 \pm 0.09 \pm 0.13 ( random and systematic errors ) .
The abundances of the other elements , except lithium , seem to be consistent with solar values .
Lithium abundances are in agreement with the “ cosmic ” ^ { 7 } Li abundance , except for two stars which show a \log \epsilon ( \mathrm { Li } ) in the range 3.6–3.7 ( although almost consistent within the error bars ) .
There are also other two stars with \log \epsilon ( \mathrm { Li } ) \sim 2.75 .
We derived an average radial velocity of the \sigma Orionis cluster of 28 \pm 4 { km } \ > { s } ^ { -1 } .

Conclusions : The \sigma Orionis metallicity is roughly solar .