The Indian Ocean island of 1.4 million people has had 641 confirmed coronavirus cases with 10 deaths, according to the latest World Health Organization (WHO) data.
All residents and visitors have been asked to stay at home or in their hotels until March 25, the agency said in a statement.
"We have decided to implement the nationwide lockdown to make sure that there is no risk of it spreading further," said Nilen Vencadasmy, chairman of the Mauritius Tourism Promotion Authority.
"Mauritius is looking forward to welcoming visitors back later in 2021 in the knowledge that we are a safe and secure destination."
The agency said Mauritius' vaccination program against the coronavirus has been underway since January, offering Oxford/AstraZeneca shots free of charge.