Context : Recent metallicity determinations in young open clusters and star-forming regions suggest that the latter may be characterized by a slightly lower metallicity than the Sun and older clusters in the solar vicinity .
However , these results are based on small statistics and inhomogeneous analyses .
The Gaia-ESO Survey is observing and homogeneously analyzing large samples of stars in several young clusters and star-forming regions , hence allowing us to further investigate this issue .

Aims : We present a new metallicity determination of the Chamaeleon I star-forming region , based on the products distributed in the first internal release of the Gaia-ESO Survey .

Methods:48 candidate members of Chamaeleon I have been observed with the high-resolution spectrograph UVES .
We use the surface gravity , lithium line equivalent width and position in the Hertzsprung-Russell diagram to confirm the cluster members and we use the iron abundance to derive the mean metallicity of the region .

Results : Out of the 48 targets , we confirm 15 high probability members .
Considering the metallicity measurements for 9 of them , we find that the iron abundance of Chamaeleon I is slightly subsolar with a mean value [ Fe/H ] = -0.08 \pm 0.04 dex .
This result is in agreement with the metallicity determination of other nearby star-forming regions and suggests that the chemical pattern of the youngest stars in the solar neighborhood is indeed more metal-poor than the Sun .
We argue that this evidence may be related to the chemical distribution of the Gould Belt that contains most of the nearby star-forming regions and young clusters .

Conclusions :