People arriving into the UK from other countries after June 8 will need to self-isolate for 14 days, the country's interior minister has announced.
"Penalties" will also be handed to people caught breaking the new guidelines, including a fixed fine of £1,000 (€1,118), or a block from entering the country for overseas nationals.
Repeated breaches of the guidelines could lead to a person being prosecuted.
Border force officials will also be carrying out "spot-checks" at the UK border, and further checks will take place from mid-June to ensure people are self-isolating for the full two weeks.
"We are taking [the measure] at a time it will be most effective," UK interior minister Priti Patel said as she announced the new restrictions on Friday.
She added that since the rate of transmission on domestic cases had lowered significantly, it was now time for the UK to focus on limiting the spread of "imported cases" and to avoid a second peak.
The UK is one of the worst-hit countries in the world by COVID-19, with more than 36,000 deaths - 351 of which occurred in the last 24 hours.
Patel said the new restrictions on travellers would be reviewed every three weeks, adding there would be a small number of exceptions - although she did not elaborate on who these were.
"We're serious about saving lives and controlling the virus," she said, earlier adding: "Now we are passed the peak of this virus, we must take steps against imported cases."
Border Force director-general Paul Lincoln later laid out four measures the agency would be implementing as the new measures come into effect.
- Increasing communications to ensure people coming to the UK understand the measures
- Asking travellers to fill in an online form prior to travel, giving contact details, travel plans and details of accommodation where they will be self-isolating
- Carrying out spot checks at the border, where any issue will lead to a passenger being required to fill out another form, or possibly be refused entry
- Imposing penalties: £100 (€111) for failing to fill out the form, and £1,000 (€1,118) for failing to self-isolate for two weeks