The problems of climate change and economic inequality are connected in multiple ways. Carbon inequality means that some individuals generate multiple times larger annual carbon emissions than others. Income and wealth disparities are main drivers of carbon inequality. Little is known how citizens perceive carbon inequality and related aspects, nor whether such perceptions are consequential for attitudes to (progressive) climate mitigation policies. Here we study such perceptions and policy attitudes through an online survey for Spain. Using quota sampling, we collected data from a sample of 3009 citizens from all regions of the country. Public perceptions of carbon inequality are measured in a qualitative and numerical way. When asked for a qualitative judgment, many people state that they perceive moderate to large differences in carbon footprints. When asked for a numerical judgment, the picture becomes more complex: comparing public perceptions with academic research data, it appears that many people actually tend to over- rather than underestimate the magnitude of footprint differences. Nevertheless, most people are aware that footprint differences are related to income differences. We also examine respondents’ attitudes to addressing carbon inequality in general in the context of climate policy, as well as to specific policy instruments with an explicit inequality dimension (wealth taxation, higher top income tax rate, frequent flyer tax, private jet ban), as well as several other instruments whose link to inequality is less obvious (e.g. carbon-border tariff). We find that a qualitatively stronger perception of the existence of carbon inequality is consistently and significantly associated with more support for all eight policy instruments. Left-wing political orientation, worry about climate change, and to a lesser extent household income are further significant predictors of favorable attitudes to several policies.