The World Record of ‘smallest hamsters’ has been achieved by the Roborovski hamsters (Phodopus roborovskii) from Russia and Kazakhstan.

Roborovski hamsters or Robos are the smallest hamster averaging under 2 cm (1 inch) at birth and between 4.5–5 cm (2 inches) and 20-25 g (1 oz) during adulthood.