We report on the surprisingly high metallicity measured in two absorption systems at high redshift , detected in the Very Large Telescope spectrum of the afterglow of the gamma-ray burst GRB 090323 . The two systems , at redshift z = 3.5673 Â and z = 3.5774 Â ( separation \Delta v \approx 660 km s ^ { -1 } ) , are dominated by the neutral gas in the interstellar medium of the parent galaxies . From the singly ionized zinc and sulfur , we estimate oversolar metallicities of [ Zn/H ] = +0.29 \pm 0.10 and [ S/H ] = +0.67 \pm 0.34 , in the blue and red absorber , respectively . These are the highest metallicities ever measured in galaxies at z > 3 . We propose that the two systems trace two galaxies in the process of merging , whose star formation and metallicity are heightened by the interaction . This enhanced star formation might also have triggered the birth of the GRB progenitor . As typically seen in star-forming galaxies , the fine-structure absorption Si ii ^ { * } is detected , both in G0 and G1 . From the rest-frame UV emission in the GRB location , we derive a relatively high , not corrected for dust extinction , star-formation rate SFR \approx 6 M _ { \odot } yr ^ { -1 } . These properties suggest a possible connection between some high-redshift GRB host galaxies and high- z massive sub-millimeter galaxies , which are characterized by disturbed morphologies and high metallicities . Our result provides additional evidence that the dispersion in the chemical enrichment of the Universe at high redshift is substantial , with the existence of very metal rich galaxies less than two billion years after the Big Bang .