He is meeting with First Minister Arlene Foster and Deputy First Minister Michelle O’Neill at Hillsborough Castle, where he will later have his first face-to-face meeting with Taoiseach Michéal Martin.
This is also Mr Johnson’s first visit to Northern Ireland since the coronavirus pandemic struck.
He is expected to outline the first stage of plans to mark the centenary of Northern Ireland’s foundation.
Discussions are also expected to take place around the response to Covid-19, rebuilding the economy and Brexit.
Arriving at Hillsborough Castle in Co Down earlier, Mr Johnson was greeted by Northern Ireland Secretary Brandon Lewis before exchanging pleasantries with the First and Deputy First Ministers on the veranda in the gardens.
Ms O’Neill inquired after his baby son Wilfred, to which Mr Johnson responded that he is “starting to verbalise and make noises”.
Asked by Mr Lewis how he was sleeping, Mr Johnson replied it was “not an issue”, adding that the baby “goes out like a light”.
A forum and historical advisory panel will work alongside the Government to commemorate the anniversary.
Speaking ahead of his visit, the Prime Minister said: “As we mark 100 years since the creation of Northern Ireland, it is important that we celebrate its people, culture and traditions, along with its vital contribution to the United Kingdom.”
Mr Johnson said the pandemic had demonstrated the strength of the UK and that Westminster and Stormont have worked closely together to get through the crisis.
He promised these close ties will continue.
“As the country begins to get back on its feet in the wake of coronavirus, we cannot simply strive to rebuild, but we must commit to building back stronger than ever.
“I cannot overstate how important the close co-operation that we have seen between central and devolved government will continue to be to this.
“Together, we will make sure Northern Ireland is ready to take full advantage of the many opportunities that lie ahead and that no part of Northern Ireland is left behind.”
The Northern Ireland Executive will receive £2.2 billion additional funding this year for its Covid-19 response.
The Treasury has also protected more than 316,000 jobs and granted thousands of business loans.
Mr Lewis said the centenary year would promote the region on a world stage.
“I am delighted that the Prime Minister is in Northern Ireland today, and has announced the first stage of our plans to mark this centenary,” he said.
“This is a fantastic opportunity for people right across the UK to celebrate Northern Ireland and its integral place within our Union.
“We will use the centenary next year to promote it on the world stage, celebrating its people, culture, traditions and enterprise and its vital contribution to the United Kingdom.”
