Michelle Mitchell is to succeed Sir Harpal Kumar as chief executive of Cancer Research UK.
During her time at the MS Society, she has overseen a 40 per cent increase in access to effective MS treatments and the charity has launched a £100m fundraising campaign.
Mitchell, a prolific tweeter and a non-executive director of NHS England, was appointed OBE in 2015.
In an interview with Third Sector in 2014, she said: "I am not someone who comes into organisations and continues with the status quo."
She said in a statement today: "It’s a privilege to be appointed as chief executive of the world’s leading charity dedicated to beating cancer through research.
"Like many people, I have family that has been affected by cancer and I’m passionate about CRUK's goal to speed up impact on survival.
"I have admired the work of the charity for many years and I look forward to leading it as we embark on the next chapter of our critically important mission."
Kumar, who has been at the helm of Britain's largest fundraising charity since 2007, announced in October that he would step down this year, and is due to leave in June. He was knighted in the 2016 New Year's Honours list for services to cancer research.
CRUK's income was £679m in the financial year ending 31 March 2017, according to accounts filed with the Charity Commission. It was £537m in 2013.
Mitchell will be paid £244,000 a year, the same as Kumar.
A CRUK spokeswoman said CRUK salaries were positioned between the median of the charitable and corporate sectors.
She said: "To achieve the charity’s ambition - that by 2034 three in four people in the UK will survive cancer for 10 years or more - it is critical to attract and retain high-calibre senior leaders as well as skilled and experienced people across a range of business functions in addition to research."
A starting date for Mitchell is yet to be confirmed, the spokeswoman said.
Sir Leszek Borysiewicz, chair of CRUK, described Mitchell as "an outstanding and seasoned charity leader, with the skill and ambition to lead the charity in the next phase of achieving our vision of three in four people surviving cancer by 2034".
Mitchell's sector roles also include board positions at the health think tank the King’s Fund and Power to Change, a trust that supports community businesses in England.
She has a BA in economics, an MA in politics and administration and an international executive diploma from Insead.