The 2020–21 Singapore circuit breaker measures were a stay-at-home order and cordon sanitaire implemented as a preventive measure by the Government of Singapore in response to the COVID-19 pandemic in the country on 7 April 2020.

A stay-at-home order, safer-at-home order, movement control order – also referred to by loose use of the terms quarantine, isolation, or lockdown – is an order from a government authority that restricts movements of a population as a mass quarantine strategy for suppressing or mitigating an epidemic or pandemic by ordering residents to stay home except for essential tasks or for work in essential businesses. The medical distinction between such an order and a quarantine is that a quarantine is usually understood to involve isolating only selected people who are considered to be possibly infectious rather than the entire population of an area. In many cases, outdoor activities are allowed. Non-essential businesses are either closed or adapted to remote work. In some regions, it has been implemented as a round-the-clock curfew or called a shelter-in-place order, but it is not to be confused with a shelter-in-place situation.