He took the oath of office a few minutes to 1pm.
Former President Uhuru Kenyatta handed his former deputy a copy of the Constitution promulgated in 2010 and a ceremonial sword. With that, the symbolic transfer of power was done.
President Ruto sought to immediately begin a new chapter away from the leadership of Uhuru, announcing new policies and review of other Jubilee regime policies such as the Competency Based Curriculum (CBC).
Ruto's speech spoke largely to the strength of the Constitution, singling out the Independent Electoral and Boundaries Commission (IEBC) and its chairman Wafula Chebukati for doing the right thing under exceptionally challenging circumstances.
"As an institution, they have set a new standard in public service that is uncompromising, professional and exemplary, raising the bar of integrity of our public officials and institutions," he said.
Ruto was declared winner of last month's elections but his victory was challenged by his competitor Raila Odinga. The Supreme Court last week ruled that he was validly elected.
The president struck a conciliatory note with supporters of Raila, promising to leave no one behind.
"Their supporters will be my constituents. I will work with all Kenyans irrespective of who they voted for," he said.
Ruto praised the resilience of the Judiciary and IEBC for standing firm against threats.
As a result, he said, one of his first acts as Head of State would be to appoint the six judges that his predecessor had overlooked. The six were picked by the Judicial Service Commission three years ago but Uhuru left them out, citing integrity issues.
He also said he will increase the Judiciary Fund by Sh3 billion annually.
Also on Ruto's list of first acts is financial independence of the police which he said would end weaponisation of security agencies and better handling of graft cases.
"The Inspector General of Police is undermined by funding dependence. As I'm making this address, I have instructed transfer of budget from the Office of the President. The IG will be the custodian of the funds," he said.
"This will ensure there is a financial independence of police to help fight corruption and finish political weaponisation of graft cases," he added.
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But some of the recent changes that ordinary Kenyans will feel from a new government taking over could be in the price of fuel and the price of flour.
Ruto said that the interventions to control the price of fuel have been unsustainable.
Uhuru's attempt to subsidise Unga in the run up to the election gobbled up Sh7 billion in one month but still had no impact, said Ruto.
More alarming was the cost of fuel subsidy. Taxpayers have spent a total of Sh144 billion, Sh60 billion in the last four months alone.
"If the subsidy continues to the end of the financial year, it will cost the taxpayer Sh280 billion, equivalent to the entire national government development budget," said Ruto.
Ruto also pledged to support IEBC's capacity by expanding its technology deployment to cover all areas of elections.
He further said he will form an education reforms task force to review CBC and advise on its fate before January 2023.
Ruto's inauguration was attended by a number of African Heads of State among them Ethiopian Prime Minister Abiy Ahmed, Somalia's President Hassan Sheikh Mohamud, Tanzania's Samia Suluhu, Malawi's Lazarus Chakwera and Burundi's Evariste Ndayishimiye.
Others were Rwanda's Paul Kagame, Eswatini Prime Minister Cleophas Dlamini Guinea Bissau's Umaro Embalo, Seychelles' Wavel Ramkalawan and President of the Union of Comoros Azali Assoumani
Uganda President Yoweri Museveni was also present, as was Djibouti's Ismail Omar Guelleh, Congo's Felix Tshisikedi, Zimbabwe's Emmerson Mnangagwa, Mozambique's Filipe Nyusi and Sierra Leone's Julius Maada Bio, The Sahrawi Arab Democratic Republic (SADR) President Brahim Ghali, and South Sudan President Salva Kiir
The African Union Commission Chair Faki Mahamat was also in attendance.
There were uncomfortable moments when Gachagua rose to speak.
The deputy president hit out at Uhuru, describing their swearing in as the return of democracy and freedom of association.
"I want to tell the people of Kenya that today is a great day. Kenya is now a democratic country," he said.
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