Mitigating climate change requires an urgent transition of the oil and gas industry. We develop two typologies of the corporate strategy and diversification options for international oil companies (IOCs) in the sustainable energy transition. Data from semi-structured interviews with oil industry professionals are thematically analysed and considered in the context of the wider literature. The resulting framework of corporate strategy options is more comprehensive than has been previously published. We find gaps in the companies' strategic readiness for the energy transition, especially in preparing for the ramp-down of the fossil fuel-based core business. Diversification options are evaluated in terms of the fit between different strategies and companies' capabilities. Many diversification options fit at least some of the existing capabilities of oil majors, but while there is potential for the companies to contribute positively to the energy transition, the current scale of change remains inadequate for meeting global climate goals. The strategic dilemma that the energy transition creates for IOCs is an essentially existential one. Future research should investigate whether IOCs can and should play an active part in the sustainable energy transition and how to drive the necessary action.