The head of the United Kingdom is the Prime Minister. As of my last knowledge update in October 2023, the Prime Minister is Rishi Sunak. However, it's important to note that the UK also has a monarch, who, as of that time, is King Charles III. The roles of the Prime Minister and the monarch are different:
To summarize, the head of the government is the Prime Minister, while the monarch serves as the head of state. If you have any further questions about the UK government or its leaders, feel free to ask!