This Review discusses crucial areas related to the identification, clinical presentation, course, and therapeutic management of bipolar disorder, a major psychiatric illness. Bipolar disorder is often misdiagnosed, leading to inappropriate, inadequate, or delayed treatment. Even when bipolar disorder is successfully diagnosed, its clinical management presents several major challenges, including how best to optimise treatment for an individual patient, and how to balance the benefits and risks of polypharmacy. We discuss the major unmet needs in the diagnosis and management of bipolar disorder in this Review, including improvement of adequate recognition and intervention in at-risk and early-disease stages, identification of reliable warning signs and prevention of relapses in unstable and rapid cycling patients, treatment of refractory depression, and prevention of suicide. Taken together, there are several promising opportunities for improving treatment of bipolar disorder to deliver medical care that is more personalised.