Sick leave (or paid sick days or sick pay) is paid time off from work that workers can use to stay home to address their health needs without losing pay. It differs from paid vacation time or time off work to deal with personal matters, because sick leave is intended for health-related purposes. Sick leave can include a mental health day and taking time away from work to go to a scheduled doctor's appointment. Some policies also allow paid sick time to be used to care for sick family members, or to address health and safety needs related to domestic violence or sexual assault. Menstrual leave is another type of time off work for a health-related reason, but it is not always paid.

In most nations, some or all employers are required to pay their employees for some time away from work when they are ill. Most European, many Latin American, a few African and a few Asian countries have legal requirements for paid sick leave for employees. In nations without laws mandating paid sick leave, some employers offer it voluntarily or as the result of a collective bargaining agreement. However, in countries with poorer labor laws such as South Korea, employees are usually forced to use paid vacation time for sick leaves, and the sick leaves exceeding the remaining vacation time are unpaid.

Even where sick leave is normally required for all employees, the business owner may not be considered an employee or have access to paid sick leave, especially in a microbusiness that is operated by the owners.

Paid sick leave can reduce employee turnover, increase productivity, and reduce the spread of disease in the workplace and in the community.