Johnson said the lockdown would close down pubs, bars and restaurants except for takeout and delivery service through Dec. 2.
Shops for food and other essential items and schools will remain open throughout the lockdown.
The prime minister said this means everyone should stay at home except for essential activities, such as medical reasons, providing care for vulnerable people, work, exercise, recreation, picking up essential items, escaping from harm and school.
Johnson also said that "exclusive support bubbles," including interactions with one other household outside the main household, could continue.
"I'm under no illusions how difficult this will be for businesses, and I'm truly sorry for that," Johnson said.
Johnson previously resisted lockdown measures, but said it's "absolutely vital to act now to save lives."
Prior to his announcement, Johnson's COVID-19 scientific advisors reviewed models showing hospitalizations and deaths could get worse than the peak in the first wave in the spring without action.
Britain reported 24,405 new coronavirus cases and 274 deaths for Friday. The country has had more than 1 million cases and 46,000 deaths since the start of the pandemic, according to The New York Times' global coronavirus tracker.
Meanwhile, Brazilian Health Minister Eduardo Pazuello has been hospitalized for dehydration after testing positive for COVID-19 last week.
Pazuello was admitted to the hospital in the capital of Brasilia on Friday for medical exams and doctors said the minister was dehydrated, CNN Brazil reported.
The Health Ministry denied that a COVID-19 complication caused the hospitalization.
Pazuello is the third health minister President Jair Bolsonaro has appointed after the first two clashed with Bolsonaro over how to handle the pandemic. Pazuello has supported the president.
Bolsonaro and dozens of Cabinet members and elected officials have tested positive for COVID-19 since the pandemic began.
The United States is the current epicenter of he pandemic, with over 9 million cases and over 229,000 deaths, according to Johns Hopkins data.
Germany on Saturday announced a new daily record of 19,059 COVID-19 cases amid a second wave of the virus across Europe.
The new restrictions will come into effect Monday, including closing restaurants, bars, gyms and theaters, Merkel said.
Germany has reported 527,916 cases and 10,469 deaths since the pandemic began, Johns Hopkins data shows.
Ukraine also reported a daily record of 8,752 new cases for Friday, the national security council said, up from 8,312 new cases reported for Thursday.
"In my opinion, based on various factors in our country, including economic ones, a complete lockdown we should avoid it as much as possible" Maksym Stepanov said in a Kyiv briefing on Friday, UNIAN reported.
Instead of a shutdown, the government has imposed certain restrictions on business, according to UNIAN.
Ukraine has reported 399,330 cases and 7,399 deaths to date, according to the Johns Hopkins data.
Other countries across Europe are tightening restrictions as COVID-19 cases surge across the continent.
Austria announced Saturday it would impose a night-time curfew and close all but take-away service at cafes, bars and restaurants as COVID-19 levels approach an unsustainable level in hospitals, according to the government.
The country similarly had a lockdown during the first wave of infection in March.
"We did not take this decision lightly but it is necessary," Austrian Chancellor Sebastian Kurz told reporters at a news conference announcing the new COVID-19 restrictions.
The new restrictions will take effect from Tuesday through the end of November and will include a curfew from 8 p.m. to 6 a.m.
Secondary schools and universities will move to remote learning, and hotels will close to all but business travelers, Kurz added, but restrictions will fall short of a total lockdown as shops, industry, kindergarten and primary schools remain open.
Austria has reported over 104,000 COVID-19 cases and 1,109 deaths from the coronavirus.
In France, the government restored a lockdown Friday, which ordered people to stay at home except for essential work or medical reasons.
The lockdown was needed because the country risked being "overwhelmed by a second wave that no doubt will be harder than the first," President Emmanuel Macron said.
Over the past 24 hours, France has reported 49,215 new COVID-19 cases, compared with 47,637 new cases on Thursday and 36,437 new cases on Wednesday.
France has reported over 1.3 million cases and 36,605 deaths since the pandemic began, according to the global tracker.
Belgium also restored a lockdown on Friday.
The lockdown came after scientists and officials heading up efforts to control COVID-19 said that the government's already tight restrictions were failing as deaths doubled every six days.
"Our country is in a health emergency," said Alexander De Croo, Belgium's prime minister. "The pressure on hospitals is immense, our care providers are making inhuman efforts. In the past week, 100,000 of our fellow countrymen were infected, we do not see any change ... We are moving to a stricter lockdown."
From Monday, the government in Belgium has ordered all non-essential businesses closed for six weeks, including hairdressers. Supermarkets will be the only businesses allowed to sell essential items.
Belgium has reported 412,314 cases and 11,452 deaths to date, according to Johns Hopkins data.
Earlier this week, the European Center for Disease Control and Prevention said Belgium had the highest number of COVID-19 infections per 100,000 people in Europe.
German Health Minister Jens Spahn said the country would open its hospitals to neighboring countries for as long at it could with intensive care units under strain in many countries, including in Belgium.
Belgium transferred some of its first patients to Germany on Thursday.
Italy reported a record 26,831 COVID-19 new daily infections Thursday, the highest daily total since the beginning of the pandemic.
Still, protesters have taken to the streets in the past week in various cities across Italy to protest new lockdown measures, including the closing of theatres, gyms and swimming pools and the closing or restaurants and bars at 6 p.m.
Prime Minister Giuseppe Conte said he wants to give the new measures a couple weeks to take effect before deciding whether to order a full shutdown similar to France.
Authorities arrested about 20 people in Florence, Italy, amid protests against lockdown measures. The restrictions sparked protests in Rome, Milan, Naples and Turin earlier this week, including violence and vandalism, and riot police firing teargas at groups of young people hurling bottles and rocks.
Italy has reported 647,674 COVID-19 cases and 38,321 COVID-19 deaths since the start of the pandemic, Johns Hopkins data shows.
Other countries across Europe, including Scotland, Slovakia, and Greece, have also imposed new coronavirus restrictions as cases surge.
Worldwide, COVID-19 has infected over 45 million people and killed over 1 million people.