Sajid Javid was appointed as Health Secretary on Saturday night after Matt Hancock quit his role having breached social distancing rules.
Mr Javid will return to lead the Covid-19 response having resigned as chancellor last year over a power struggle with No 10.
Bringing Mr Javid back into government means that Boris Johnson can avoid a wider shake up of his ministerial team following Mr Hancock’s departure.
As well as overseeing the Government’s response to Covid-19, Mr Javid will be tasked with devising major reforms to the funding and provision of social care.
His appointment was announced shortly before 8pm on Saturday night – less than two hours after Mr Hancock’s resignation was made public.
Downing Street said: "The Queen has been pleased to approve the appointment of the Rt Hon Sajid Javid MP as Secretary of State for Health and Social Care."
The Department of Health and Social Care will be the sixth government department that Mr Javid has run, after previous posts as chancellor, home secretary, housing secretary, business secretary and culture secretary.
Mr Javid resigned as chancellor in February 2020 after being told his entire team of advisers would be sacked and replaced with Number 10 appointees in a joint economic unit – an ultimatum he said “no self-respecting minister” could accept.
Mr Javid’s appointment was immediately welcomed by figures including Ruth Davidson, the former leader of the Scottish Conservatives, and Lord Macpherson, the ex permanent secretary of the Treasury.
Lord Macpherson said: "’The Saj’ is a good appointment. Experienced. Sensible. Happy to stand up to officials (and Prime Ministers). Full of integrity. From middle England. In short, a grown up."
Ms Davidson said she was "really pleased" to see Mr Javid back in government.