Acute kidney injury (AKI) and fluids are closely linked through oliguria, which is a marker of the former and a trigger for administration of the latter. Recent progress in this field has challenged the physiological and clinical rational of using oliguria as a trigger for the administration of fluid and brought attention to the delicate balance between benefits and harms of different aspects of fluid management in critically ill patients, in particular those with AKI. This narrative review addresses various aspects of fluid management in AKI outlining physiological aspects, the effects of crystalloids and colloids on kidney function and the effect of various resuscitation and de-resuscitation strategies on the course and outcome of AKI.