We study the effect of the light rare earth ions La, Ce, Pr, and Nd on electronic structure, structural properties, magnetic states, and ferroelectric properties of BiFeO 3 using density functional theory within GGA ? U method. The supercell of 40 atoms is considered for four phases: R3c, Pnma, Pn2 1 a, Pbam. We show that, among potential phases, the R3c-G structure of BiFeO 3 where one Bi substituted by one of the studied rare-earth elements has the minimal total energy. We predict the values of spontaneous electric polarization in RE-doped BiFeO 3 to be above 80 lC cm -2 and a non-zero values of the magnetic moments in RE-doped BiFeO 3 for R3c-G phase of the studied systems. Upon introduction of a rare-earth ion to a Bi site, the total magnetic moments are 0 l B , 0.99, 1.99, and 2.98 l B f.u. -1 for La, Ce, Pr, and Nd substitution, respectively. The results of total energy calculations show that the Pn2 1 a and Pnma phases of the BiFeO 3 with Ce or Pr substitution of Bi occur on the same energy scale. This close energy scale suggests a coexistence of these phases beyond T = 0 K or under other conditions.