  Evidence for the presence of quasi-periodic oscillations (QPOs) in the
optical polarization of the blazar PKS 2155-304, during a period of enhanced
gamma-ray brightness, is presented. The periodogram of the polarized flux
revealed the existence of a prominent peak at $T\sim 13$ min, detected at
>99.7% significance, and $T\sim 30$ min, which was nominally significant at
>99%. This is the first evidence of QPOs in the polarization of an active
galactic nucleus, potentially opening up a new avenue of studying this
phenomenon.
