The Sub-Millimetre Radiometer (SMR), on board the Odin satellite, observed a major stratospheric sudden warming (SSW) in the northern hemisphere in early January 2013. The provided measurements have been used to identify and characterize this event which seems to be the strongest of that kind in recent years. This paper is based on a comparison with the 2009 SSW which was so far considered as a record-breaking event. SSWs are an important manifestation of the coupling phenomena between the mesosphere / lower thermosphere and the lower atmospheric layers and can strongly affect the middle atmospheric composition. It is crucial to study these events in order to get a better understanding of the dynamical and chemical mechanisms that control this part of the atmosphere.