A new lanthanum oxychromate (LaO) 2CrO 4 has been successfully synthetized by ceramic route under oxygen flow. Its crystal structure was determined ab‐initio from X‐ray and neutron diffraction data (space group C2/c No.15; a = 14.3884(4)Å, b = 4.4107(1)Å, c = 8.4849(2)Å, β= 107.016(3)°; Z = 4; reliability factors: R p = 9.16%, R wp = 12.1%; χ 2 = 5.02, R bragg = 5.24%,R exp. = 5.42%). It consists in the stacking of distorted chromate and LaO layers along the a axis. The structure of (LaO) 2CrO 4 was found similar to those of sulfates Grandreefite (PbF) 2SO 4 and (LaO) 2SO 4.