The Ukrainian President announced that he will be in the capital for “face-to-face” talks with the Prime Minister.
The leaders are expected to discuss the UK’s support of Ukraine in its fight against Vladimir Putin’s army.
In a tweet, Mr Zelensky said: “Today – London. The UK is a leader when it comes to expanding our capabilities on the ground and in the air.
“This cooperation will continue today. I will meet my friend Rishi. We will conduct substantive negotiations face-to-face and in delegations.”
Andriy Yermak from Mr Zelensky’s office added more detail about the trip to London.
In a post on Telegram, he said: “Today there are important meetings in London. We are working on strengthening the defence of Ukraine and supporting our progress with Nato.”
Mr Zelensky is expected to attend the next major Nato summit in person, with Ukraine pushing for a timeline for it joining the alliance.
The President last visited London in February, when he also met King Charles III and addressed MPs in Westminster Hall.
