Stimulated Raman emission in the terahertz frequency range (4.8–5.1 THz and 5.9–6.5 THz) has been realized by optical excitation of arsenic donor centers in silicon at low temperatures. The Stokes shift of the observed laser emission is 5.42 THz which is equal to the Raman-active donor electronic transition between the ground 1s(A1) and the excited 1s(E) arsenic states. Optical thresholds of the Raman laser are similar to those observed for other silicon donor lasers. In addition, intracenter donor lasing has been observed when pumping on the dipole-forbidden 1s(A1)?2s transition.