The observation of the bottom, strange baryon Ξ0b through the decay chain Ξ0b→Ξ+cπ−, where Ξ+c→Ξ−π+π+, Ξ−→Λπ−, and Λ→pπ−, is reported by using data corresponding to an integrated luminosity of 4.2  fb−1 from pp collisions at s√=1.96  TeV recorded with the Collider Detector at Fermilab. A signal of 25.3+5.6−5.4 candidates is observed whose probability of arising from a background fluctuation is 3.6×10−12, corresponding to 6.8 Gaussian standard deviations. The Ξ0b mass is measured to be 5787.8±5.0(stat)±1.3(syst)  MeV/c2. In addition, the Ξ−b baryon is observed through the process Ξ−b→Ξ0cπ−, where Ξ0c→Ξ−π+, Ξ−→Λπ−, and Λ→pπ−.