The Prime Minister flies to Philadelphia, where she will address Republican Senators and Congress members, before meeting Donald Trump at the White House on Friday.
Mrs May, the first world leader to hold face-to-face talks with President Trump since his inauguration, has told MPs she is pleased to be able to meet him so early in his administration.
She wants to talk to the President about deepening the economic and commercial relationship between the two countries post-Brexit and signing a UK-US trade deal once the UK has left the EU.
Also on the White House agenda will be strengthening defence and security co-operation between the two countries and through NATO, countering the menace of Islamic State and creating conditions for peace in Syria.
While she is in Washington, Mrs May will also visit Arlington National Cemetery - where members of the British military who died fighting alongside US forces are buried - to lay a wreath at the Tomb of the Unknown Soldier.
The PM is flying straight to Philadelphia, where she will address the annual congressional Republican Retreat, becoming the first serving head of government or state from outside the US to do so.
As well as addressing the Republicans' "congressional retreat", she will also hold talks with Paul Ryan, Speaker of the House of Representatives, and Mitch McConnell, the Senate Majority Leader.
In her speech at the Republican event, the Prime Minister will talk about her desire and belief in the need to renew the special relationship, claiming it is important not only to Britain and America but to the world.
"The leadership provided by our two countries through the Special Relationship has done more than win wars and overcome adversity," she is expected to say.
"It made the modern world.
"The institutions upon which that world relies were so often conceived or inspired by our two nations working together.
"So as we rediscover our confidence together - as you renew your nation just as we renew ours - we have the opportunity - indeed the responsibility - to renew the special relationship for this new age.
"We have the opportunity to lead, together, again."
But the Prime Minister's decision to go to Philadelphia, cradle of American independence, and only address Republican members of the Senate and Congress has infuriated Democrats in Washington.
Although the Democrats are currently at their own retreat, it is claimed that her snub is unprecedented and may not be good tactics come the US mid-term elections in two years, when the UK will need support on Capitol Hill as it seeks a trade deal requiring approval in Congress.