Rubbing-induced molecular alignment and its relaxation in polystyrene (PS) thin films are studied with optical birefringence. A novel relaxation of the alignment is observed that is distinctly different from the known relaxation processes of PS. First, it is not the Kohlrausch-Williams-Watts type but instead is characterized by two single exponentials plus a temperature-dependent constant. At temperatures several degrees or more below the glass-transition temperature (T-g), the relaxation time falls between that of the a and beta relaxations. Second, the decay time constants are the same within 40% for PS with weight-average molecular weights (M-w's) of 13,700-550,000 Da at temperatures well below the sample T-g 's, indicating that the molecular relaxations involved are mostly local within the entanglement distance. Nonetheless, the temperature at which the rubbing-induced molecular alignment disappears (TO) exhibits a strong M-w dependence and closely approximates the T-g of the sample. Furthermore, To depends notably on the thickness of the polymer in much the same way as previously found for the T-g of supported PS films. This suggests that the a process becomes dominant near T-g. Preliminary spectroscopic studies in the mid-infrared range show a significant degree of bending of the phenyl ring toward the sample surface, with the C-C bond connecting the phenyl ring and the main chain tends to lie along the rubbing direction, which indicates that the relaxation is connected with the reorientation of this C-C bond. We exclude the observed relaxation, as predominantly a near-surface one, because detailed studies on the effects of rubbing conditions on the degree of molecular alignment indicate that the alignment is not local to the polymer-air surface.