Аннотация:A search for charmless four-body decays of Λ0b and Ξ0b baryons with a proton and three charged mesons (either kaons or pions) in the final state is performed. The data sample used was recorded in 2011 and 2012 with the LHCb experiment and corresponds to an integrated luminosity of 3 fb−1. Six decay modes are observed, among which Λ0b → pK−π+π−, Λ0b → pK−K+K−, Ξ0b → pK−π+π− and Ξ0b → pK−π+K− are established for the first time. Their branching fractions (including the ratio of hadronisation fractions in the case of the Ξ0b baryon) are determined relative to the Λ0b → Λ+c π− decay.