The resonance Raman spectra of mass-selected chromium trimers (Cr₃) in argon matrices have been obtained. Five resonance Raman transitions were observed between 450 nm and 690 nm. Four of them are assigned to a totally symmetric (a₁') vibrational progression, from which we obtain a ground state harmonic frequency of w_e = 432.2 cm^-1 with w_ec_e = 16.3 cm^-1.  The other Raman line, observed at 302.0 cm^-1, is assigned to the degenerate bending motion n₂(e') of the triatomic metal cluster. The geometry of the ground state is that of an equilateral triangle (D_3h). These results provide a value of the stretching force constant of k_e = 1.91 mdyne/Å and a spectroscopic atomization energy of 0.36 eV.