Johnson, the former foreign secretary, secured 92,153 votes against 46,656 of his rival Jeremy Hunt in the battle for 10 Downing Street.
Indian-origin Labour Party candidates won more seats than their rival Conservatives.
Johnson becomes the 14th Prime Minister to be appointed by Queen Elizabeth II, the 55th to hold the post of British PM and the third in fairly quick succession since Britain voted to leave the EU in June 2016 - following on from David Cameron and Theresa May.
United Kingdom will go to the polls on Thursday. This election is being dubbed the most unpredictable of all time.
The United Kingdom has voted by 51.9 per cent to 48.1 per cent to leave the European Union after 43 years in an historic referendum.