We revealed that the dwarf nova 1RXS J232953.9+062814 is an SU UMa-type system with a superhump period of 66.774 \pm 0.010 { min } .
The short period strongly indicates that the orbital period of this object is below the period minimum of cataclysmic variables .
The superhump period is 4.04 \pm 0.02 % longer than the photometric period during quiescence ( 64.184 \pm 0.003 min ) , which is probably associated with the orbital period .
Although the standard evolutionary scenario of cataclysmic variables predicts lower mass-transfer rates in systems with shorter orbital periods , we revealed firm evidence of a relatively high mass-transfer rate from its large proper motion and bright apparent magnitude .
Its proximity indicates that we have overlooked a number of objects in this new class .
With the analogous system of V485 Cen , these objects establish the first subpopulation in hydrogen-rich cataclysmic variables below the period minimum .