The prime minister has led the tributes to Prince Philip, who has died at the age of 99.
Speaking from Downing Street, Mr Johnson said: "He [Philip] was an environmentalist, and a champion of the natural world long before it was fashionable.
"With his Duke of Edinburgh awards scheme he shaped and inspired the lives of countless young people and at literally tens of thousands of events he fostered their hopes and encouraged their ambitions.
"We remember the duke for all of this and above all for his steadfast support for Her Majesty the Queen.
"Not just as her consort, by her side every day of her reign, but as her husband, her ‘strength and stay’, of more than 70 years."
Labour leader Sir Keir Starmer, said: "The United Kingdom has lost an extraordinary public servant in Prince Philip.
"Prince Philip dedicated his life to our country – from a distinguished career in the Royal Navy during the Second World War to his decades of service as the Duke of Edinburgh.
"However, he will be remembered most of all for his extraordinary commitment and devotion to The Queen.
"For more than seven decades, he has been at her side. Their marriage has been a symbol of strength, stability and hope, even as the world around them changed – most recently during the pandemic."
Scotland’s First Minister Nicola Sturgeon tweeted: "I am saddened by news that the Duke of Edinburgh has died.
"I send my personal and deepest condolences – and those of @scotgov and the people of Scotland – to Her Majesty The Queen and her family."
Mark Drakeford, the first minister of Wales, said: "Throughout his long and distinguished life, he served the crown with selfless devotion and generosity of spirit.
"He will be missed by the many organisations that he supported as patron or president over many decades of service."
Northern Ireland’s First Minister Arlene Foster said: "He had a strong interest in Northern Ireland and I had the privilege of meeting him on a number of his many visits here.
"He had a profound and positive impact on thousands of our young people who found their purpose, passion and place in the world through participation in the Duke of Edinburgh Awards."
Scott Morrison, the prime minister of Australia, said in a statement: "Through his service to the Commonwealth he presided as patron or president of nearly 50 organisations in Australia.
"Given his own service, Prince Philip also had a strong connection with the Australian Defence Force.
"For 65 years, The Duke of Edinburgh’s Award scheme has encouraged over 775,000 young Australians to explore their leadership potential.
"Forty thousand young Australians are currently participating in the program.
"Australians send our love and deepest condolences to her Majesty and all the Royal Family."
Indian Prime Minister Narendra Modi, said: "He had a distinguished career in the military and was at the forefront of many community service initiatives. May his soul rest in peace."
Canada’s Prime Minister Justin Trudeau described Prince Philip as a "man of great purpose and conviction".
"Prince Philip contributed so much to the social fabric of our country – and the world," he tweeted.
"He will be remembered as a decorated naval officer, a dedicated philanthropist, and a constant in the life of Queen Elizabeth II.
"The thoughts of all Canadians are with her and the entire Royal Family as they mourn this significant loss.
Former prime minister Tony Blair said: "Our whole nation will be united in sadness at the passing of Prince Philip.
"He will naturally be most recognised as a remarkable and steadfast support to the Queen over so many years. However, he should also be remembered and celebrated in his own right as a man of foresight, determination and courage.
"He was often way ahead of his time in protection of the environment, in reconciliation between religious faiths and of course in the creation of the Duke of Edinburgh’s Award."
Former US president George W Bush has praised the Duke of Edinburgh’s devotion to worthy causes and to others.
In a statement issued on behalf of himself and his wife Laura, Mr Bush said: "He represented the United Kingdom with dignity and brought boundless strength and support to the sovereign.
"Laura and I are fortunate to have enjoyed the charm and wit of his company, and we know how much he will be missed."