We show that sleep deprivation exerts a strong negative effect on labour market performance. We exploit variations in child sleep quality to instrument for parental sleep quality drawing from British survey data, and variations in region specific sleep determinants on German data. A one-hour reduction in sleep duration and quality significantly decreases labour force participation, the number of hour�s worked and household income. In addition, in the British sample we find that low-skilled mothers are more likely to opt out of the labour market and work less hours than high-skilled mothers when exposed to sleep deprivation. We argue that sleep is a major determinant of employment outcomes that needs more attention in designing economic models of time allocation and employment policies. |