When is the geomagnetic field going to reverse? This question is always asked at public outreach events concerning geomagnetism and palaeomagnetism and it is one to which the answer is invariably “we don’t know”. This session aims to stimulate discussion on this important topic and bring scientists up-to-date on current thinking. From direct observations of the geomagnetic field we know that it is weakening globally and becoming less dipolar. But these observations span a very short time in the history of the Earth. From palaeomagnetism we know that the field has undergone many similar transitions in the past, some leading to reversals and some not, but we have poor knowledge of the details of such transitions. Geodynamo simulations also can be very useful to understand future directions of the present geomagnetic field. We solicit contributions from both the geomagnetism and palaeomagnetism communities, together with planetary science scientists, that help answer this important question. Contributions that consider the implications of such a decay for space weather are also welcome.